Long-Lived Assets - Schedule of Finite-Lived Intangible Assets (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Client contracts
Summary of carrying value of assets
Gross Carrying Amount	$ 135,488	$ 130,573
Accumulated Amortization	(88,585)	(75,382)
Net Amount	46,903	55,191
Client contracts | Investments in client contracts
Summary of carrying value of assets
Gross Carrying Amount	34,657	27,370
Accumulated Amortization	(23,907)	(20,345)
Net Amount	10,750	7,025
Client contracts | Capitalized costs
Summary of carrying value of assets
Gross Carrying Amount	6,667	5,003
Accumulated Amortization	(3,463)	(3,340)
Net Amount	3,204	1,663
Client contracts | Acquired client contracts
Summary of carrying value of assets
Gross Carrying Amount	94,164	98,200
Accumulated Amortization	(61,215)	(51,697)
Net Amount	32,949	46,503
Software
Summary of carrying value of assets
Gross Carrying Amount	131,529	121,069
Accumulated Amortization	(86,797)	(77,504)
Net Amount	44,732	43,565
Software | Acquired software
Summary of carrying value of assets
Gross Carrying Amount	67,012	67,975
Accumulated Amortization	(56,806)	(53,820)
Net Amount	10,206	14,155
Software | Internal use software
Summary of carrying value of assets
Gross Carrying Amount	64,517	53,094
Accumulated Amortization	(29,991)	(23,684)
Net Amount	$ 34,526	$ 29,410