Business Segment Information - Operating Results by Business Segment (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014
Operating results by business segment
Managed care and other revenue	$ 775,031	$ 751,589	$ 699,861	$ 676,461	$ 863,506	$ 809,249	$ 776,240	$ 748,650	$ 2,902,942		$ 3,197,645		$ 2,968,374
PBM and dispensing	488,354	540,543	464,484	440,561	405,237	380,833	381,367	232,318	1,933,942		1,399,755		791,744
Cost of care	(472,211)	(480,243)	(472,529)	(457,631)	(587,816)	(596,323)	(568,288)	(522,328)	(1,882,614)		(2,274,755)		(2,088,595)
Cost of goods sold	(456,658)	(509,673)	(436,930)	(415,459)	(381,817)	(360,444)	(361,409)	(218,207)	(1,818,720)		(1,321,877)		(732,949)
Direct service costs and other	$ (240,985)	$ (229,094)	$ (214,077)	$ (192,456)	$ (205,901)	$ (220,586)	$ (191,455)	$ (204,450)	(876,612)	[1],[2],[3]	(822,392)	[1],[2],[3]	(723,498)	[1],[2],[3]
Stock compensation expense									37,422		50,384		40,584
Changes in fair value of contingent consideration									(104)		44,257		6,172
Impairment of intangible assets									4,800
Less: non-controlling interest segment profit (loss)									(737)		(2,634)		(5,087)
Segment profit (loss)									301,793		275,651		266,919
Operating segments | Healthcare
Operating results by business segment
Managed care and other revenue									2,659,685		2,959,252		2,780,905
Cost of care									(1,882,614)		(2,274,755)		(2,090,352)
Direct service costs and other									(573,706)		(510,811)		(485,388)
Stock compensation expense									4,440		8,502		6,654
Changes in fair value of contingent consideration									(231)		(1,404)		38
Impairment of intangible assets									4,800
Less: non-controlling interest segment profit (loss)									(567)		(2,439)		(5,087)
Segment profit (loss)									212,941		183,223		216,944
Operating segments | Pharmacy Management
Operating results by business segment
Managed care and other revenue									243,561		238,456		205,524
PBM and dispensing									2,053,188		1,510,180		844,512
Cost of care													(16,298)
Cost of goods sold									(1,933,086)		(1,427,680)		(784,758)
Direct service costs and other									(261,570)		(284,968)		(200,198)
Stock compensation expense									20,509		36,351		29,767
Changes in fair value of contingent consideration									127		45,661		6,134
Segment profit (loss)									122,729		118,000		84,683
Corporate and Elimination
Operating results by business segment
Managed care and other revenue									(304)		(63)		(18,055)
PBM and dispensing									(119,246)		(110,425)		(52,768)
Cost of care													18,055
Cost of goods sold									114,366		105,803		51,809
Direct service costs and other									(41,336)		(26,613)		(37,912)
Stock compensation expense									12,473		5,531		4,163
Less: non-controlling interest segment profit (loss)									(170)		(195)
Segment profit (loss)									$ (33,877)		$ (25,572)		$ (34,708)

[1] Includes changes in fair value of contingent consideration of $6,172, $44,257 and $(104) for the years ended December 31, 2014, 2015 and 2016, respectively.

[2] Includes impairment of intangible assets of $4,800 for the year ended December 31, 2016.

[3] Includes stock compensation expense of $40,584, $50,384 and $37,422 for the years ended December 31, 2014, 2015 and 2016, respectively.