General - Revenues and Significant Customers (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Net revenues
Managed Care Revenue	$ 644,900	$ 576,800	$ 1,851,200	$ 1,692,600
Fee-For-Service, Fixed Fee and Cost-Plus Contracts Revenue	156,100	143,700	444,000	349,300
Rebate Revenues	21,400	22,000	64,900	63,100
PBM Revenue	419,300	413,700	1,288,200	1,110,700
Dispensing Revenue	49,800	57,500	158,200	167,200
Medicare Part D Revenues	131,800	76,500	367,900	192,000
Co-payments	15,800	7,200	55,500	24,300
Medicare Part D Receivables	170,500		170,500		$ 117,500
Revenues	$ 1,419,406	$ 1,292,132	$ 4,144,168	3,573,499
Florida Medicaid Contract
Net revenues
Termination notice			1 day
Termination notice period without cause			30 days
Florida Contracts
Net revenues
Revenues			$ 457,700	403,400
Pharmacy Management | Customer A
Net revenues
Revenues			3,709	261,094
Pharmacy Management | Customer B
Net revenues
Revenues			$ 266,795	$ 78,471