Goodwill - Intangibles (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Apr. 01, 2017	Dec. 31, 2017
Finite And Indefinite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 564,241		$ 549,916
Accumulated Amortization	(215,863)		(263,701)
Net	348,378		$ 286,215
Amortization of Intangible Assets	$ 13,520	$ 12,900
Customer Relationships [Member]
Finite And Indefinite Lived Intangible Assets [Line Items]
Weighted-Average Life	10 years		10 years
Gross Carrying Amount	$ 454,492		$ 440,167
Accumulated Amortization	(211,062)		(259,337)
Net	$ 243,430		$ 180,830
Developed Technology [Member]
Finite And Indefinite Lived Intangible Assets [Line Items]
Weighted-Average Life	5 years		5 years
Gross Carrying Amount	$ 6,340		$ 6,340
Accumulated Amortization	(3,360)		(3,043)
Net	$ 2,980		$ 3,297
Other Intangible Assets [Member]
Finite And Indefinite Lived Intangible Assets [Line Items]
Weighted-Average Life	5 years		5 years
Gross Carrying Amount	$ 2,409		$ 2,409	[1]
Accumulated Amortization	(1,441)		(1,321)	[1]
Net	968		1,088	[1]
Trade Names [Member]
Finite And Indefinite Lived Intangible Assets [Line Items]
Gross Carrying Amount	101,000		101,000
Accumulated Amortization	0		0
Net	$ 101,000		$ 101,000

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