Intangible Assets (Details) $ in Thousands		12 Months Ended
		Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($) Years	Dec. 31, 2015 USD ($)
Finite And Indefinite Lived Intangible Assets [Line Items]
Gross carrying amount		$ 549,916	$ 593,037
Accumulated amortization		(263,701)	(256,155)
Intangible assets, net		286,215	336,882
Amortization of Intangible Assets		50,071	$ 54,886	$ 51,036
Future Amortization Expense, Year One		40,916
Future Amortization Expense, Year Two		34,497
Future Amortization Expense, Year Three		28,492
Future Amortization Expense, Year Four		22,534
Future Amortization Expense, Year Five		$ 20,462
Customer Relationships [Member]
Finite And Indefinite Lived Intangible Assets [Line Items]
Weighted Average Useful Life		10 years	10 years
Gross carrying amount		$ 440,167	$ 476,176
Accumulated amortization		(259,337)	(247,206)
Intangible assets, net		$ 180,830	$ 228,970
Patented Technology [Member]
Finite And Indefinite Lived Intangible Assets [Line Items]
Weighted Average Useful Life		5 years	5 years
Gross carrying amount		$ 6,340	$ 9,140
Accumulated amortization		(3,043)	(4,435)
Intangible assets, net		$ 3,297	4,705
Amortizable trade names [Domain]
Finite And Indefinite Lived Intangible Assets [Line Items]
Weighted Average Useful Life		5 years
Gross carrying amount		$ 2,409
Accumulated amortization		(1,321)
Intangible assets, net		1,088
Other Intangible Assets [Member]
Finite And Indefinite Lived Intangible Assets [Line Items]
Gross carrying amount	[1]		6,721
Accumulated amortization	[1]		(4,514)
Intangible assets, net	[1]		$ 2,207
Acquired Finite-lived Intangible Asset, Useful Life, Minimum | Years			2
Acquired Finite-lived Intangible Asset, Useful Life, Maximum | Years			5
Trade Names [Member]
Finite And Indefinite Lived Intangible Assets [Line Items]
Gross carrying amount		101,000	$ 101,000
Accumulated amortization		0	0
Intangible assets, net		$ 101,000	$ 101,000

[1] Consists of non-competition agreements with useful lives ranging from two to five years.