Other Intangible Assets, Net (Schedule of Finite-Lived Intangible Assets by Major Class) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Other intangible assets, gross	$ 610,475		$ 607,791
Less accumulated amortization	(268,635)		(255,643)
Total	341,840		352,148
Amortization expense for finite-lived intangible assets	11,700	$ 9,800
Client lists
Finite-Lived Intangible Assets [Line Items]
Other intangible assets, gross	498,380		496,192
Less accumulated amortization	(229,879)		(219,887)
Total	268,501		276,305
Non-compete agreements
Finite-Lived Intangible Assets [Line Items]
Other intangible assets, gross	9,312		9,302
Less accumulated amortization	(8,155)		(7,983)
Total	1,157		1,319
Trade names and licenses
Finite-Lived Intangible Assets [Line Items]
Other intangible assets, gross	102,783		102,297
Less accumulated amortization	(30,601)		(27,773)
Total	$ 72,182		$ 74,524