Accounting Policies [Abstract] Accounting Policies [Abstract] Accounts Notes And Loans Receivable [Line Items] Accounts, Notes, Loans and Financing Receivable [Line Items] Accounts Payable Accrued Liabilities And Other Liabilities Disclosure Noncurrent [Text Block] Other Non-Current Liabilities Accounts Payable Current Accounts payable Accounts Receivable Net Current Accounts receivable, net Accrued Bonuses Current Discretionary bonus Accrued Income Taxes Current Income taxes payable (Note 13) Accrued Income Taxes Noncurrent Non-current income taxes payable (Note 13) Accrued Utilities Current Facility related liabilities Accumulated Amortization, Capital Government Grants Accumulated Amortization Capital Government Grants Less accumulated amortization Accumulated Depreciation Depletion And Amortization Property Plant And Equipment Less accumulated depreciation and asset write off Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Currency Impact on Long Term Funding , Effect Pretax Accumulated Other Comprehensive Income Loss Cumulative Changes In Currency Impact On Long Term Funding Effect Pretax Currency impact on long term funding Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Currency Impact on Long Term Funding, Tax Accumulated Other Comprehensive Income Loss Cumulative Changes In Currency Impact On Long Term Funding Tax Tax on currency impact on long term funding Accumulated Other Comprehensive Income Loss Defined Benefit Pension And Other Postretirement Plans Net Of Tax Net actuarial loss Actuarial loss on defined benefit pension plan (note 9) Accumulated Other Comprehensive Income Loss Foreign Currency Translation Adjustment Net Of Tax Currency translation adjustments Accumulated Other Comprehensive Income Loss [Line Items] Accumulated Other Comprehensive Income (Loss) [Line Items] Accumulated Other Comprehensive Income Loss Net Of Tax Accumulated other comprehensive income (Note 19) Total Accumulated Other Comprehensive Income (Loss), Other Net Unrealized Gains Losses On Securities Accumulated Other Comprehensive Income Loss Other Net Unrealized Gains Losses On Securities Unrealised capital gain(loss) - investments (note 3) Accumulated Other Comprehensive Income Loss [Table] Accumulated Other Comprehensive Income (Loss) [Table] Disclosure of the components of accumulated other comprehensive income (loss). Accumulated Other Comprehensive Income Loss [Text Block] Accumulated Other Comprehensive Income Accumulated Other Comprehensive Income [Member] Accumulated Other Comprehensive Income Acquired Finite Lived Intangible Assets [Line Items] Acquired Finite-Lived Intangible Assets [Line Items] Additional Paid In Capital Common Stock Additional paid-in capital Additional Paid In Capital [Member] Additional Paid-in Capital Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value Share based compensation expense Adjustments To Additional Paid In Capital Stock Issued Issuance Costs Share issue costs Adjustments To Additional Paid In Capital Tax Effect From Share Based Compensation Excess tax benefit on exercise of equity compensation Tax benefit on exercise of options Adjustments To Reconcile Net Income Loss To Cash Provided By Used In Operating Activities [Abstract] Adjustments to reconcile net income to net cash provided by operating activities: Adjustment To Additional Paid In Capital Income Tax Effect From Share Based Compensation Net [Abstract] Impact on shareholders equity and other comprehensive income of the tax consequence of : Adjustment to Retained Earning Share Repurchase costs Adjustment To Retained Earning Share Repurchase Costs Share repurchase costs Advertising Costs Policy [Text Block] Advertising Costs Allocated Share Based Compensation Expense Share-based compensation Allowance for doubtful accounts amounts released during the year. Allowance For Doubtful Accounts Other Amounts released during the year Allowance for Doubtful Accounts, Provisions Allowance For Doubtful Accounts Provisions Amounts provided during the year Allowance For Doubtful Accounts Receivable Closing provision Opening provision Allowance For Doubtful Accounts Receivable Write Offs Amounts used during the year Allowance for Doubtful Accounts, Table Allowance For Doubtful Accounts Table [Text Block] Provision for Doubtful Debts Allowance For Doubtful Accounts [Text Block] Allowance For Doubtful Accounts [Text Block] Provision for Doubtful Debts Amendment Flag Amendment Flag The amortization of capital government grants which are amortized and recognized in earnings over the grant period. Amortization Of Government Grants Government grants amortized to the profit and loss account Amortization Of Intangible Assets Amortization of intangibles Amount amortized in the period since the date of acquisition Asset Impairment Charges Impairment charge Assets Assets Total Assets Assets [Abstract] ASSETS Assets Current Total current assets Assets Current [Abstract] Current Assets: Assets Noncurrent [Abstract] Other Assets: Available For Sale Securities Debt Securities Current At end of year At start of year Short term investments - available for sale (Note 3) Available For Sale Securities, Debt Securities Current, Additions Available For Sale Securities Debt Securities Current Additions Additions Available For Sale Securities, Debt Securities Current, Disposals Available For Sale Securities Debt Securities Current Disposals Disposals Available For Sale Securities Disclosure Available For Sale Securities Disclosure [Text Block] Short Term Investments - Available for Sale Availableforsale Securities Gross Unrealized Gain Loss 1 Unrealized capital gain/(loss) - investments Award Type [Axis] Award Type Baillie Gifford Diversified Growth Fund [Member] Baillie Gifford Diversified Growth Fund [Member] Baillie Gifford Diversified Growth Fund Basis Point Increase In Pension And Postretirement Benefits Discount Rate Basis Point Increase In Pension And Postretirement Benefits Discount Rate Basis point increase in benefits obligation discount rate BeijingWits Medical Limited [Member] Beijing Wits Medical Limited [Member] BeijingWits Medical Limited Building [Member] Building Buildings And Improvements Gross Building Business Acquisition Acquiree [Domain] Business Acquisition, Acquiree [Domain] Business Acquisition [Axis] Business Acquisition Business Acquisition [Line Items] Business Acquisition [Line Items] Business Acquisition Percentage Of Voting Interests Acquired Percentage of common stock acquired Business Acquisition Pro Forma Earnings Per Share Basic Basic earnings per share Business Acquisition Pro Forma Earnings Per Share Diluted Diluted earnings per share Business Acquisition Pro Forma Information [Text Block] Proforma Effect in Net Revenue Net Income and Earnings Per Share Business Acquisition, Purchase Price Allocation, Deferred Income Tax Liabilities Business Acquisition Purchase Price Allocation Deferred Income Tax Liabilities Deferred tax liability Business Acquisition Purchase Price Allocation Working Capital Business Acquisition Purchase Price Allocation Working Capital Working capital adjustment Working capital adjustment Business Acquisitions Pro Forma Net Income Loss Net income Business Acquisitions Pro Forma Revenue Net revenue Business Combination Consideration Transferred 1 Amount of total consideration Business Combination Contingent Consideration Arrangements Cash Payment Made Business Combination Contingent Consideration Arrangements Cash Payment Made Further consideration paid in relation to certain performance milestones achieved Business Combination Contingent Consideration Arrangements Change In Amount Of Contingent Consideration Liability 1 Reduction in additional consideration Business Combination Contingent Consideration Liability Contingent consideration Acquisition consideration payable Additional consideration Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Cash And Equivalents Cash and cash equivalents Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Contingent Liability Contingent consideration Liability arising from contingent consideration arrangement Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Current Assets Other Other current assets Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Current Assets Prepaid Expense And Other Assets Prepayments and other current assets Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Current Assets Receivables Accounts receivable Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Current Liabilities Other Current liabilities Other liabilities Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Intangibles Intangible asset Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Noncurrent Liabilities Other Non-current other liabilities Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Other Noncurrent Assets Non-current assets Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Property Plant And Equipment Property, plant and equipment Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Unbilled Revenue Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Unbilled Revenue Unbilled revenue Business Combination Recognized Identifiable Assets Acquired Goodwill And Liabilities Assumed Net Net assets acquired Net assets acquired Net assets acquired Net assets acquired Net assets acquired Business Combinations [Abstract] Business Combinations [Abstract] Business Combinations Policy Business Combinations Capital Government Grants Current Capital Government Grants Current Less current portion Noncurrent capital government grants, which are amortized and recognized in earnings over the grant period. Capital Government Grants Noncurrent Non-current government grants Non-current government grants (Note 11) Capitalized Computer Software Gross Computer equipment and software Capital Redemption Reserve Capital Redemption Reserve Capital redemption reserve (Note 12 (a)) Capital Redemption Reserve Capital Redemption Reserve [Member] Capital Redemption Reserve Cash Acquired From Acquisition Cash acquired with subsidiary undertaking Cash And Cash Equivalents At Carrying Value Cash and cash equivalents at end of year Cash and cash equivalents at beginning of year Cash and cash equivalents Cash And Cash Equivalents Period Increase Decrease Net increase/(decrease) in cash and cash equivalents Cash And Cash Equivalents Policy [Text Block] Cash and Cash Equivalents Cash Flow Supplemental Disclosures [Text Block] Supplemental Disclosure of Cash Flow Information Cash [Member] Cash Clinical trial services [Member] Clinical Trial Services [Member] Clinical Trial Services Commitments And Contingencies Disclosure [Abstract] Commitments and Contingencies Disclosure [Abstract] Commitments And Contingencies Disclosure [Text Block] Commitments and Contingencies Common Stock [Member] Ordinary Shares Common Stock Par Or Stated Value Per Share Ordinary shares, par value Common Stock Shares Authorized Ordinary shares, shares authorized Common Stock Shares Issued Ordinary shares, shares issued Common Stock Shares Outstanding Ordinary shares, shares outstanding Common Stock Value Ordinary shares, par value 6 euro cents per share; 100,000,000 shares authorized, (Note 12) 61,587,257 shares issued and outstanding at December 31, 2013 and 60,287,498 shares issued and outstanding at December 31, 2012. Common Stock Voting Rights Share allotment description Compensation And Retirement Disclosure [Abstract] Compensation and Retirement Disclosure [Abstract] Compensation Related Costs Policy [Text Block] Direct Costs Compensation Related Costs Share Based Payments Disclosure [Line Items] Compensation Related Costs Share Based Payments Disclosure [Line Items] Compensation Related Costs Share Based Payments Disclosure [Line Items] Compensation Related Costs Share Based Payments Disclosure [Table] Compensation Related Costs Share Based Payments Disclosure [Table] Compensation Related Costs Share Based Payments Disclosure [Table] Comprehensive Income Net Of Tax Total comprehensive income Total comprehensive income Comprehensive Income Net Of Tax [Abstract] Comprehensive Income: Computer Equipment and Capitalized Software [Member] Computer Equipment And Capitalized Software [Member] Computer equipment and software Concentration Risk Percentage 1 Clients which represented 10% or more of the company's net revenue Consolidation Policy [Text Block] Basis of Consolidation Contracts Revenue Gross revenue Corporate Bonds [Member] Corporate Bonds [Member] Iboxx Corporate Bond Cost Of Goods And Services Sold Direct costs Cost Of Reimbursable Expense Reimbursable expenses Cost Of Revenue [Abstract] Costs and expenses: Cost Of Sales [Member] Direct costs Costs And Expenses Total costs and expenses Current Fiscal Year End Date Current Fiscal Year End Date Current Income Tax Expense Benefit Current tax Current Income Tax Expense Benefit Continuing Operations [Abstract] Current: Customer A [Member] Customer A [Member] Client A Customer B [Member] Customer B [Member] Client B Customer Lists [Member] Volunteer list acquired Customer Relationships [Member] Customer relationships acquired Debt Securities [Member] Bonds Deferred Income Taxes And Tax Credits Deferred taxes Deferred Income Tax Expense Benefit Deferred tax expense/(benefit) Deferred Income Tax Expense Benefit Continuing Operations [Abstract] Deferred expense/(benefit): Deferred Items Grants From Outside Parties Deferred Items Grants From Outside Parties Received Deferred Revenue And Credits Deferred Revenue and Credits Deferred Revenue And Credits Current Short term government grants (note 11) Deferred Revenue Current Payments on account Deferred Tax Assets Gross Total deferred tax assets Deferred Tax Assets Liabilities Net Net deferred tax asset Deferred Tax Assets Net Deferred tax assets recognized Deferred Tax Assets Net [Abstract] Deferred tax assets: Deferred Tax Assets Net Current Deferred tax asset (Note 13) Deferred Tax Assets Net Noncurrent Non-current deferred tax asset (Note 13) Deferred Tax Assets Operating Loss Carryforwards Net operating loss carry forwards Deferred Tax Assets Operating Loss Carryforwards Not Subject To Expiration Non-U.S subsidiaries Operating loss carry forwards for income tax Deferred Tax Assets Operating Loss Carryforwards Subject To Expiration Additional operating loss carry forward Net operating loss carryforward Deferred Tax Assets Property Plant And Equipment Property, plant and equipment Deferred Tax Assets Tax Credit Carryforwards Alternative Minimum Tax Alternative minimum tax credit carry forwards Deferred Tax Assets Tax Credit Carryforwards General Business Business credit carry forwards that are available to offset Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Deferred compensation expense Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Other Stock compensation Deferred Tax Assets Tax Deferred Expense Other Other Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Accrued Liabilities Accrued expenses and payments on account Deferred Tax Assets Unrealized Currency Losses Unrealised FX Deferred Tax Assets Valuation Allowance Valuation allowance for deferred tax assets Valuation allowance for deferred tax assets Deferred Tax Liabilities Total deferred tax liabilities recognized Deferred Tax Liabilities [Abstract] Deferred tax liabilities: Deferred Tax Liabilities Current Deferred tax liability (Note 13) Deferred Tax Liabilities Deferred Expense Reserves And Accruals Accruals Deferred Tax Liabilities Goodwill And Intangible Assets Goodwill Deferred Tax Liabilities Noncurrent Non-current deferred tax liability (Note 13) Deferred Tax Liabilities Other Other Deferred Tax Liabilities Other Finite Lived Assets Other intangible assets Deferred Tax Liabilities Property Plant And Equipment Property, plant and equipment Deferred Tax Liabilities Undistributed Foreign Earnings Deferred tax liability unrecognized for the undistributed earnings of foreign subsidiaries Deferred Tax Liabilities Unrealized Currency Transaction Gains Unrealised FX Defined Benefit Pension Plan Liabilities Noncurrent Defined benefit pension obligations, net (note 9) Defined Benefit Pension Plans [Axis] Defined Benefit Pension Plans [Axis] Defined Benefit Pension Plans [Axis] Defined Benefit Pension Plans [Domain] Defined Benefit Pension Plans [Domain] Defined Benefit Pension Plans [Domain] Defined Benefit Plan Accumulated Other Comprehensive Income Loss After Tax Total Defined Benefit Plan Actual Return On Plan Assets Actual return on plan assets Defined Benefit Plan, Actual Return on Plan Assets Percentage Defined Benefit Plan Actual Return On Plan Assets Percentage Risk free interest rate Defined Benefit Plan Actuarial Gain Loss Actuarial loss Defined Benefit Plan, Actuarial Losses to be Amortized and Reclassified from Accumulated Other Comprehensive Income (Loss) to Net Pension Cost Defined Benefit Plan Actuarial Losses To Be Amortized And Reclassified From Accumulated Other Comprehensive Income Loss To Net Pension Cost Actuarial loss - benefit obligation Defined Benefit Plan Amortization Of Gains Losses Amortization of net loss Defined Benefit Plan Amount Of Change In Basis Points Used To Determine Overall Expected Long Term Rate Of Return On Assets Assumption Defined Benefit Plan Amount Of Change In Basis Points Used To Determine Overall Expected Long Term Rate Of Return On Assets Assumption Basis points increase to determine log-term expected return on bonds Defined Benefit Plan Amounts Recognized In Balance Sheet Non-current other liabilities Defined Benefit Plan Assumptions Used Calculating Benefit Obligation Discount Rate Discount rate Defined Benefit Plan Assumptions Used Calculating Benefit Obligation Rate Of Compensation Increase Rate of compensation increase Defined Benefit Plan Assumptions Used Calculating Net Periodic Benefit Cost Discount Rate Discount rate Defined Benefit Plan Assumptions Used Calculating Net Periodic Benefit Cost Expected Long Term Return On Assets Expected long-term rate of return on assets Expected rate of return on plan assets Defined Benefit Plan Assumptions Used Calculating Net Periodic Benefit Cost Rate Of Compensation Increase Rate of compensation increase Defined Benefit Plan Assumptions Used In Calculations Narrative Description Discount Rate Description Defined Benefit Plan Benefit Obligation Benefit obligation at end of year Benefit obligation at beginning of year Defined Benefit Plan Benefits Paid Benefits paid Defined Benefit Plan By Plan Asset Categories [Axis] Defined Benefit Plan, Asset Categories [Axis] Defined Benefit Plan Contributions By Employer Employer contributions Defined Benefit Plan Contributions By Plan Participants Contributions Plan participants' contributions Defined Benefit Plan Contributions [Member] Defined Benefit Plan Contributions [Member] Defined Benefit Plan Contributions Defined Benefit Plan Disclosure [Line Items] Defined Benefit Plan Disclosure [Line Items] Defined Benefit Plan Expected Future Benefit Payments Five Fiscal Years Thereafter Expected future benefit payments in Years 2018 - 2022 Defined Benefit Plan Expected Future Benefit Payments Next Twelve Months Expected future benefit payments in 2014 Defined Benefit Plan Expected Future Benefit Payments Remainder Of Fiscal Year Expected future benefit payments in 2013 Defined Benefit Plan Expected Future Benefit Payments Year Four Expected future benefit payments in 2017 Defined Benefit Plan Expected Future Benefit Payments Year Three Expected future benefit payments in 2016 Defined Benefit Plan Expected Future Benefit Payments Year Two Expected future benefit payments in 2015