Business Segment Information - Operating Results by Business Segment (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Operating results by business segment
Net revenue	$ 1,254,118	$ 1,170,117	$ 3,636,535	$ 3,392,571
Cost of care	(437,308)	(364,438)	(1,247,234)	(1,035,377)
Cost of goods sold	(546,337)	(560,269)	(1,559,221)	(1,621,577)
Direct service costs and other	(238,471)	(216,770)	(713,065)	(620,767)
Legal matter settlement			9,000
Stock compensation expense	5,974	5,442	19,384	17,831
Segment Profit (Loss)	37,976	34,082	145,399	132,681
Managed care and other
Operating results by business segment
Net revenue	668,591	568,688	1,970,708	1,670,567
PBM
Operating results by business segment
Net revenue	585,527	601,429	1,665,827	1,722,004
Healthcare
Operating results by business segment
Net revenue	580,278	489,451	1,698,427	1,459,378
Pharmacy Management
Operating results by business segment
Net revenue	677,339	685,928	1,948,919	1,948,203
Operating Segments | Healthcare
Operating results by business segment
Cost of care	(437,308)	(364,438)	(1,247,234)	(1,035,377)
Direct service costs and other	(123,843)	(104,610)	(365,577)	(310,996)
Stock compensation expense	1,465	833	5,919	4,696
Segment Profit (Loss)	20,592	21,236	91,535	117,701
Operating Segments | Healthcare | Managed care and other
Operating results by business segment
Net revenue	580,278	489,451	1,698,427	1,459,378
Operating Segments | Pharmacy Management
Operating results by business segment
Cost of goods sold	(549,472)	(565,121)	(1,568,998)	(1,635,380)
Direct service costs and other	(101,037)	(91,012)	(310,189)	(252,960)
Legal matter settlement			9,000
Stock compensation expense	2,125	1,615	7,167	5,661
Segment Profit (Loss)	28,955	31,410	85,899	65,524
Operating Segments | Pharmacy Management | Managed care and other
Operating results by business segment
Net revenue	88,488	79,382	272,761	211,684
Operating Segments | Pharmacy Management | PBM
Operating results by business segment
Net revenue	588,851	606,546	1,676,158	1,736,519
Corporate and Eliminations
Operating results by business segment
Cost of goods sold	3,135	4,852	9,777	13,803
Direct service costs and other	(13,591)	(21,148)	(37,299)	(56,811)
Stock compensation expense	2,384	2,994	6,298	7,474
Segment Profit (Loss)	(11,571)	(18,564)	(32,035)	(50,544)
Corporate and Eliminations | Managed care and other
Operating results by business segment
Net revenue	(175)	(145)	(480)	(495)
Corporate and Eliminations | PBM
Operating results by business segment
Net revenue	$ (3,324)	$ (5,117)	$ (10,331)	$ (14,515)