Long-Lived Assets - Summary of Carrying Value of Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 323,366	$ 320,079
Accumulated Amortization	(251,508)	(245,614)
Net Amount	71,858	74,465
Acquired customer contracts
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	154,119	153,790
Accumulated Amortization	(107,846)	(105,778)
Net Amount	46,273	48,012
Software
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	169,247	166,289
Accumulated Amortization	(143,662)	(139,836)
Net Amount	$ 25,585	$ 26,453