Other Intangible Assets, Net (Schedule of Finite-Lived Intangible Assets by Major Class) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Gross	$ 803,299		$ 816,196
Accumulated Amortization	(438,874)		(437,378)
Net	364,425		378,818
Amortization of Intangible Assets	14,300	$ 16,600
Impairment of intangible assets		$ 0
Client lists
Finite-Lived Intangible Assets [Line Items]
Gross	650,380		662,611
Accumulated Amortization	(352,847)		(354,011)
Net	297,533		308,600
Non-compete agreements
Finite-Lived Intangible Assets [Line Items]
Gross	26,746		26,409
Accumulated Amortization	(17,565)		(16,249)
Net	9,181		10,160
Tradenames and licenses
Finite-Lived Intangible Assets [Line Items]
Gross	126,173		127,176
Accumulated Amortization	(68,462)		(67,118)
Net	$ 57,711		$ 60,058