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, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Other intangible assets, gross	$ 844,155		$ 844,155		$ 786,245
Less accumulated amortization	(353,083)		(353,083)		(307,332)
Total	491,072		491,072		478,913
Amortization expense for finite-lived intangible assets	14,900	$ 13,900	42,900	$ 38,800
Client lists [Member]
Finite-Lived Intangible Assets [Line Items]
Other intangible assets, gross	690,900		690,900		637,053
Less accumulated amortization	(292,222)		(292,222)		(257,787)
Total	398,678		398,678		379,266
Non-compete agreements [Member]
Finite-Lived Intangible Assets [Line Items]
Other intangible assets, gross	28,119		28,119		28,106
Less accumulated amortization	(14,434)		(14,434)		(11,136)
Total	13,685		13,685		16,970
Trade names and licenses [Member]
Finite-Lived Intangible Assets [Line Items]
Other intangible assets, gross	125,136		125,136		121,086
Less accumulated amortization	(46,427)		(46,427)		(38,409)
Total	$ 78,709		$ 78,709		$ 82,677