Other Intangible Assets, Net (Schedule of Finite-Lived Intangible Assets by Major Class) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Other intangible assets, gross	$ 789,213		$ 786,245
Less accumulated amortization	(323,080)		(307,332)
Total	466,133		478,913
Amortization expense for finite-lived intangible assets	14,000	$ 11,700
Client lists [Member]
Finite-Lived Intangible Assets [Line Items]
Other intangible assets, gross	639,479		637,053
Less accumulated amortization	(269,514)		(257,787)
Total	369,965		379,266
Non-compete agreements [Member]
Finite-Lived Intangible Assets [Line Items]
Other intangible assets, gross	28,108		28,106
Less accumulated amortization	(12,233)		(11,136)
Total	15,875		16,970
Trade names and licenses [Member]
Finite-Lived Intangible Assets [Line Items]
Other intangible assets, gross	121,626		121,086
Less accumulated amortization	(41,333)		(38,409)
Total	$ 80,293		$ 82,677