Other Intangible Assets, Net (Schedule of Finite-Lived Intangible Assets by Major Class) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Other intangible assets, gross	$ 788,858		$ 788,858		$ 607,791
Less accumulated amortization	(281,063)		(281,063)		(255,643)
Total	507,795		507,795		352,148
Amortization expense for finite-lived intangible assets	13,200	$ 9,800	24,900	$ 19,600
Client lists
Finite-Lived Intangible Assets [Line Items]
Other intangible assets, gross	639,404		639,404		496,192
Less accumulated amortization	(238,965)		(238,965)		(219,887)
Total	400,439		400,439		276,305
Non-compete agreements [Member]
Finite-Lived Intangible Assets [Line Items]
Other intangible assets, gross	28,113		28,113		9,302
Less accumulated amortization	(8,946)		(8,946)		(7,983)
Total	19,167		19,167		1,319
Trade names and licenses
Finite-Lived Intangible Assets [Line Items]
Other intangible assets, gross	121,341		121,341		102,297
Less accumulated amortization	(33,152)		(33,152)		(27,773)
Total	$ 88,189		$ 88,189		$ 74,524