Business Segment Information - Operating Results by Business Segment (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Operating results by business segment
Net revenue	$ 1,100,075	$ 1,154,289	$ 2,222,454	$ 2,273,295
Cost of care	(321,831)	(408,911)	(670,939)	(778,008)
Cost of goods sold	(528,067)	(501,081)	(1,061,308)	(1,027,395)
Direct service costs and other	(199,756)	(195,907)	(403,997)	(398,207)
Stock compensation expense	6,592	5,207	12,389	14,607
Segment Profit (Loss)	57,013	53,597	98,599	84,292
Managed care and other
Operating results by business segment
Net revenue	548,711	608,614	1,101,879	1,175,162
PBM
Operating results by business segment
Net revenue	551,364	545,675	1,120,575	1,098,133
Healthcare
Operating results by business segment
Net revenue	481,021	546,113	969,927	1,052,935
Pharmacy Management
Operating results by business segment
Net revenue	624,062	612,658	1,262,275	1,229,118
Operating Segments | Healthcare
Operating results by business segment
Cost of care	(321,831)	(408,911)	(670,939)	(778,008)
Direct service costs and other	(100,450)	(98,314)	(206,386)	(198,424)
Stock compensation expense	2,102	2,237	3,863	3,780
Segment Profit (Loss)	60,842	41,125	96,465	80,283
Operating Segments | Healthcare | Managed care and other
Operating results by business segment
Net revenue	481,021	546,113	969,927	1,052,935
Operating Segments | Pharmacy Management
Operating results by business segment
Cost of goods sold	(532,685)	(505,203)	(1,070,259)	(1,035,410)
Direct service costs and other	(80,082)	(78,776)	(161,948)	(158,411)
Stock compensation expense	1,939	2,124	4,046	3,796
Segment Profit (Loss)	13,234	30,803	34,114	39,093
Operating Segments | Pharmacy Management | Managed care and other
Operating results by business segment
Net revenue	67,867	62,648	132,302	122,543
Operating Segments | Pharmacy Management | PBM
Operating results by business segment
Net revenue	556,195	550,010	1,129,973	1,106,575
Corporate and Eliminations
Operating results by business segment
Cost of goods sold	4,618	4,122	8,951	8,015
Direct service costs and other	(19,224)	(18,817)	(35,663)	(41,372)
Stock compensation expense	2,551	846	4,480	7,031
Segment Profit (Loss)	(17,063)	(18,331)	(31,980)	(35,084)
Corporate and Eliminations | Managed care and other
Operating results by business segment
Net revenue	(177)	(147)	(350)	(316)
Corporate and Eliminations | PBM
Operating results by business segment
Net revenue	$ (4,831)	$ (4,335)	$ (9,398)	$ (8,442)