Other Intangible Assets, Net (Schedule of Finite-Lived Intangible Assets by Major Class) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Other intangible assets, gross	$ 790,439		$ 790,439		$ 607,791
Less accumulated amortization	(295,681)		(295,681)		(255,643)
Total	494,758		494,758		352,148
Amortization expense for finite-lived intangible assets	13,900	$ 9,400	38,800	$ 28,900
Client lists [Member]
Finite-Lived Intangible Assets [Line Items]
Other intangible assets, gross	640,612		640,612		496,192
Less accumulated amortization	(249,639)		(249,639)		(219,887)
Total	390,973		390,973		276,305
Non-compete agreements [Member]
Finite-Lived Intangible Assets [Line Items]
Other intangible assets, gross	28,110		28,110		9,302
Less accumulated amortization	(10,045)		(10,045)		(7,983)
Total	18,065		18,065		1,319
Trade names and licenses [Member]
Finite-Lived Intangible Assets [Line Items]
Other intangible assets, gross	121,717		121,717		102,297
Less accumulated amortization	(35,997)		(35,997)		(27,773)
Total	$ 85,720		$ 85,720		$ 74,524