Revenue Recognition - Disaggregation of Revenue (NET Services) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Total Service revenue, net	$ 1,509,944	$ 1,384,965	$ 1,318,220
NET Services
Disaggregation of Revenue [Line Items]
Total Service revenue, net	1,509,944	1,384,965
NET Services | State Medicaid agency contracts
Disaggregation of Revenue [Line Items]
Total Service revenue, net	736,030	732,261
NET Services | Managed care organization contracts
Disaggregation of Revenue [Line Items]
Total Service revenue, net	773,914	652,704
NET Services | Capitated contracts
Disaggregation of Revenue [Line Items]
Total Service revenue, net	1,277,241	1,096,822
NET Services | Non-capitated contracts
Disaggregation of Revenue [Line Items]
Total Service revenue, net	$ 232,703	$ 288,143