General - Customers Exceeding Ten Percent of Consolidated Net Revenues (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2020 USD ($) item	Mar. 31, 2019 USD ($)
Significant customers
Revenues	$ 1,794,307	$ 1,739,489
Maximum
Significant customers
Term of contracts with customers	3 years
Term of contract extensions or renewals	2 years
Virginia Contracts
Significant customers
Revenues	$ 232,500	193,900
CCC Plus Contract
Significant customers
Term of contracts with customers	5 years
Term of contract extensions or renewals	12 months
Termination notice	90 days
CCC Plus Contract | Maximum
Significant customers
Number of contract extensions or renewals | item	5
Medallion Contract
Significant customers
Number of contract extensions or renewals | item	6
Term of contract extensions or renewals	12 months
Termination notice	180 days
New York Contract
Significant customers
Revenues	$ 215,900	195,200
Massachusetts Contracts
Significant customers
Revenues	$ 176,000	$ 179,200
SCO Contract
Significant customers
Term of contract extensions or renewals	1 year
Termination notice	180 days
SCO Contract | Maximum
Significant customers
Number of contract extensions or renewals | item	5
CMS Contract
Significant customers
Term of contracts with customers	1 year