Long-Lived Assets - Summary of Carrying Value of Assets (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 303,753	$ 303,929
Accumulated Amortization	(210,201)	(202,073)
Net Amount	93,552	101,856
Acquired client contracts
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	147,990	148,148
Accumulated Amortization	(87,760)	(82,692)
Net Amount	60,230	65,456
Software
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	155,763	155,781
Accumulated Amortization	(122,441)	(119,381)
Net Amount	$ 33,322	$ 36,400