Business Segment Information - Operating Results by Business Segment (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Operating results by business segment
Net revenue	$ 1,170,117	$ 1,158,543	$ 3,392,571	$ 3,431,838
Cost of care	(364,438)	(397,697)	(1,035,377)	(1,175,705)
Cost of goods sold	(560,269)	(523,973)	(1,621,577)	(1,551,368)
Direct service costs and other	(216,770)	(195,844)	(620,767)	(594,051)
Stock compensation expense	5,442	4,604	17,831	19,211
Segment Profit (Loss)	34,082	45,633	132,681	129,925
Managed care and other
Operating results by business segment
Net revenue	568,688	591,229	1,670,567	1,766,391
PBM
Operating results by business segment
Net revenue	601,429	567,314	1,722,004	1,665,447
Healthcare
Operating results by business segment
Net revenue	489,451	521,379	1,459,378	1,574,314
Pharmacy Management
Operating results by business segment
Net revenue	685,928	642,054	1,948,203	1,871,172
Operating Segments | Healthcare
Operating results by business segment
Cost of care	(364,438)	(397,697)	(1,035,377)	(1,175,705)
Direct service costs and other	(104,610)	(99,416)	(310,996)	(297,840)
Stock compensation expense	833	1,995	4,696	5,775
Segment Profit (Loss)	21,236	26,261	117,701	106,544
Operating Segments | Healthcare | Managed care and other
Operating results by business segment
Net revenue	489,451	521,379	1,459,378	1,574,314
Operating Segments | Pharmacy Management
Operating results by business segment
Cost of goods sold	(565,121)	(528,500)	(1,635,380)	(1,563,910)
Direct service costs and other	(91,012)	(79,842)	(252,960)	(238,253)
Stock compensation expense	1,615	1,669	5,661	5,465
Segment Profit (Loss)	31,410	35,381	65,524	74,474
Operating Segments | Pharmacy Management | Managed care and other
Operating results by business segment
Net revenue	79,382	69,968	211,684	192,511
Operating Segments | Pharmacy Management | PBM
Operating results by business segment
Net revenue	606,546	572,086	1,736,519	1,678,661
Corporate and Eliminations
Operating results by business segment
Cost of goods sold	4,852	4,527	13,803	12,542
Direct service costs and other	(21,148)	(16,586)	(56,811)	(57,958)
Stock compensation expense	2,994	940	7,474	7,971
Segment Profit (Loss)	(18,564)	(16,009)	(50,544)	(51,093)
Corporate and Eliminations | Managed care and other
Operating results by business segment
Net revenue	(145)	(118)	(495)	(434)
Corporate and Eliminations | PBM
Operating results by business segment
Net revenue	$ (5,117)	$ (4,772)	$ (14,515)	$ (13,214)