Document and Entity Information
6 Months Ended
Jun. 30, 2019
Document And Entity Information [Abstract]  
Document Type 6-K
Amendment Flag false
Document Period End Date Jun. 30, 2019
Document Fiscal Year Focus 2019
Document Fiscal Period Focus Q2
Entity Registrant Name ICON plc
Entity Central Index Key 0001060955
Current Fiscal Year End Date --12-31