Cost in Excess of Net Assets of Companies Acquired - Intangibles (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended		6 Months Ended		12 Months Ended
		Jun. 27, 2015	Jun. 28, 2014	Jun. 27, 2015	Jun. 28, 2014	Dec. 31, 2014
Finite And Indefinite Lived Intangible Assets [Line Items]
Gross Carrying Amount		$ 624,665		$ 624,665		$ 513,561
Accumulated Amortization		(199,895)		(199,895)		(177,850)
Net		424,770		424,770		$ 335,711
Amortization of Intangible Assets		13,917	$ 10,870	25,024	$ 21,817
Amortization of intangible assets, net of tax		$ 11,169	$ 8,867	$ 20,198	$ 17,774
Amortization of intangible assets, per share basic		$ 0.12	$ 0.09	$ 0.21	$ 0.18
Amortization of intangible assets, per share diluted		$ 0.12	$ 0.09	$ 0.21	$ 0.18
Customer Relationships [Member]
Finite And Indefinite Lived Intangible Assets [Line Items]
Weighted-Average Life		10 years				10 years
Gross Carrying Amount		$ 509,735		$ 509,735		$ 402,036
Accumulated Amortization		(192,664)		(192,664)		(171,071)
Net		$ 317,071		317,071		$ 230,965
Developed Technology [Member]
Finite And Indefinite Lived Intangible Assets [Line Items]
Weighted-Average Life		5 years				5 years
Gross Carrying Amount		$ 12,994		12,994		$ 8,806
Accumulated Amortization		(6,458)		(6,458)		(5,444)
Net		6,536		6,536		3,362
Other Intangible Assets [Member]
Finite And Indefinite Lived Intangible Assets [Line Items]
Gross Carrying Amount	[1]	936		936		1,719
Accumulated Amortization	[1]	(773)		(773)		(1,335)
Net	[1]	163		163		384
Trade Names [Member]
Finite And Indefinite Lived Intangible Assets [Line Items]
Gross Carrying Amount		101,000		101,000		101,000
Accumulated Amortization		0		0		0
Net		$ 101,000		$ 101,000		$ 101,000
Minimum [Member] | Other Intangible Assets [Member]
Finite And Indefinite Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Useful Life				2 years
Maximum [Member] | Other Intangible Assets [Member]
Finite And Indefinite Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Useful Life				3 years

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