Change in Control - Schedule of Fair Value of Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Apr. 01, 2014
Assets Acquired:
Goodwill	$ 660,981	$ 660,981	$ 670,294
Merger Agreement
Assets Acquired:
Cash and cash equivalents				$ 17,845
Restricted cash				1,648
Accounts receivable				39,311
Unbilled services				13,065
Reimbursable pass-through expenses				12,184
Prepaid expenses and other current assets				12,205
Property and equipment				39,661
Goodwill				670,294
Intangible assets				306,307
Deferred income taxes				26,246
Other assets				3,237
Total assets acquired				1,142,003
Liabilities assumed:
Accounts payable and accrued expenses				16,608
Pre-funded study costs				36,483
Advanced billings				52,475
Deemed landlord liability				34,251
Debt				1,551
Deferred income taxes				69,448
Other liabilities				9,889
Total liabilities assumed				220,705
Net assets acquired				$ 921,298