Segment Information - Schedule of Selected Information for Each Reportable Segment (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Segment Reporting Information [Line Items]
Consolidated net revenues	$ 541,296	$ 450,977
Operating income (loss)	45,164	17,558
Depreciation and amortization	(23,763)	(25,003)
Stock-based compensation	(1,417)	(470)
Operating expenses	(587,115)	(500,742)
Interest income (expense), net	(55,853)	(56,463)
Gain on extinguishment of debt	221
Income (loss) before income tax (provision) benefit and income (loss) from equity investments	(10,468)	(38,905)
Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating income (loss)	79,332	48,630
Operating Segments [Member] | Clinical [Member]
Segment Reporting Information [Line Items]
Consolidated net revenues	254,859	219,664
Operating income (loss)	42,736	25,649
Operating Segments [Member] | Commercial [Member]
Segment Reporting Information [Line Items]
Consolidated net revenues	290,926	234,546
Operating income (loss)	48,920	31,879
Operating Segments [Member] | Corporate and Other [Member]
Segment Reporting Information [Line Items]
Operating income (loss)	(12,324)	(8,898)
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Consolidated net revenues	(4,489)	(3,233)
Other Unallocated Charges [Member]
Segment Reporting Information [Line Items]
Operating expenses	$ (8,988)	$ (5,599)