Segment Information - Schedule of Selected Information for Each Reportable Segment (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Segment Reporting Information [Line Items]
Consolidated net revenues	$ 489,417	$ 449,569	$ 940,394	$ 871,374
Depreciation and amortization	(23,908)	(27,072)	(48,911)	(53,582)
Stock-based compensation	(45)	(118)	(515)	(444)
Operating expenses	(542,862)	(501,969)	(1,043,604)	(971,661)
Operating income (loss)	29,632	11,642	47,190	20,068
Interest income (expense), net	(57,120)	(53,232)	(113,583)	(105,684)
Income (loss) before income tax (provision) benefit and income (loss) from equity investments	(27,488)	(41,590)	(66,393)	(85,616)
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Operating expenses	(16,996)	(11,046)	(31,096)	(22,726)
Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating income (loss)	70,581	49,878	127,712	96,820
Operating Segments [Member] | Clinical [Member]
Segment Reporting Information [Line Items]
Consolidated net revenues	233,582	218,146	453,246	432,974
Operating income (loss)	28,469	21,527	54,118	44,862
Operating Segments [Member] | Commercial [Member]
Segment Reporting Information [Line Items]
Consolidated net revenues	258,664	232,831	492,737	441,538
Operating income (loss)	42,112	28,351	73,594	51,958
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Consolidated net revenues	$ (2,829)	$ (1,408)	$ (5,589)	$ (3,138)