Property and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 385,783	$ 306,110
Accumulated depreciation and amortization	(226,929)	(189,081)
Property and equipment, net	$ 158,854	117,029
Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life of property and equipment	3 years
Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life of property and equipment	40 years
Land
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 7,138	7,138
Buildings and improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 21,373	21,143
Buildings and improvements | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life of property and equipment	5 years
Buildings and improvements | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life of property and equipment	40 years
Furniture and office equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 77,337	73,457
Furniture and office equipment | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life of property and equipment	5 years
Furniture and office equipment | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life of property and equipment	7 years
Computer hardware
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 15,684	10,173
Computer hardware | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life of property and equipment	3 years
Computer hardware | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life of property and equipment	7 years
Computer software
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 183,015	137,150
Computer software | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life of property and equipment	3 years
Computer software | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life of property and equipment	10 years
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 65,719	49,241
Leasehold improvements | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life of property and equipment	3 years
Leasehold improvements | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life of property and equipment	10 years
Construction in progress
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 15,517	$ 7,808