Long-Lived Assets - Summary of Carrying Value of Assets (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 310,243	$ 306,835
Accumulated Amortization	(228,326)	(219,204)
Net Amount	81,917	87,631
Acquired client contracts
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	149,267	148,872
Accumulated Amortization	(96,491)	(93,767)
Net Amount	52,776	55,105
Software
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	160,976	157,963
Accumulated Amortization	(131,835)	(125,437)
Net Amount	$ 29,141	$ 32,526