Long-Lived Assets - Summary of Carrying Value of Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 299,353	$ 303,929
Accumulated Amortization	(210,462)	(202,073)
Net Amount	88,891	101,856
Acquired client contracts
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	146,502	148,148
Accumulated Amortization	(88,946)	(82,692)
Net Amount	57,556	65,456
Software
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	152,851	155,781
Accumulated Amortization	(121,516)	(119,381)
Net Amount	$ 31,335	$ 36,400