General - Customers Exceeding Ten Percent of Consolidated Net Revenues (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019 USD ($) item	Mar. 31, 2018 USD ($)
Operating results by business segment
Revenues	$ 1,739,489	$ 1,805,077
Minimum
Operating results by business segment
Term of contracts with customers	1 year
Term of contract extensions or renewals	1 year
Maximum
Operating results by business segment
Term of contracts with customers	3 years
Term of contract extensions or renewals	2 years
Virginia Contracts
Operating results by business segment
Revenues	$ 193,900	117,300
CCC Plus Contract
Operating results by business segment
Term of contracts with customers	5 years
Term of contract extensions or renewals	12 months
Termination notice	90 days
CCC Plus Contract | Maximum
Operating results by business segment
Number of contract extensions or renewals | item	5
Medallion Contract
Operating results by business segment
Number of contract extensions or renewals | item	6
Term of contract extensions or renewals	12 months
Termination notice	180 days
New York Contract
Operating results by business segment
Revenues	$ 195,200	180,500
Massachusetts Contracts
Operating results by business segment
Revenues	$ 179,200	163,700
SCO Contract
Operating results by business segment
Term of contract extensions or renewals	1 year
Termination notice	180 days
SCO Contract | Maximum
Operating results by business segment
Number of contract extensions or renewals | item	5
CMS Contract
Operating results by business segment
Term of contracts with customers	1 year
Healthcare | Customer A
Operating results by business segment
Revenues	$ 62,929	152,386
Pharmacy Management | Customer B
Operating results by business segment
Revenues	$ 89,340	$ 91,442