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, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Other intangible assets, gross	$ 790,611		$ 790,611		$ 786,245
Less accumulated amortization	(337,440)		(337,440)		(307,332)
Total	453,171		453,171		478,913
Amortization expense for finite-lived intangible assets	13,900	$ 13,200	27,900	$ 24,900
Client lists [Member]
Finite-Lived Intangible Assets [Line Items]
Other intangible assets, gross	643,645		643,645		637,053
Less accumulated amortization	(280,449)		(280,449)		(257,787)
Total	363,196		363,196		379,266
Non-compete agreements [Member]
Finite-Lived Intangible Assets [Line Items]
Other intangible assets, gross	28,112		28,112		28,106
Less accumulated amortization	(13,332)		(13,332)		(11,136)
Total	14,780		14,780		16,970
Trade names and licenses [Member]
Finite-Lived Intangible Assets [Line Items]
Other intangible assets, gross	118,854		118,854		121,086
Less accumulated amortization	(43,659)		(43,659)		(38,409)
Total	$ 75,195		$ 75,195		$ 82,677