Acquisitions (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended				3 Months Ended
	Mar. 31, 2012	Apr. 02, 2011	Apr. 02, 2011 Acquisitions 2011 [Member]	Mar. 01, 2011 RFPD [Member]	Dec. 31, 2011 Nu Horizons [Member]	Apr. 02, 2011 Nu Horizons [Member]	Jan. 03, 2011 Nu Horizons [Member]
Business Acquisition [Line Items]
Business Acquisition, Cost of Acquired Entity, Purchase Price	$ 180,767	$ 175,892		$ 235,973			$ 161,125
Business Acquisition, Purchase Price Allocation, Current Assets, Cash and Cash Equivalents	7,900	22,337					18,085
Business Combination, Purchase Price Allocation, Debt Paid	4,383						26,375
Business Acquisition, Contingent Consideration, at Fair Value	14,850
Sales	4,889,529	5,223,003
Net income attributable to shareholders	113,628	136,309
Basic	$ 1.01	$ 1.18
Diluted	$ 1	$ 1.16
Business Combination, Pro Forma Information [Abstract]
Business Acquisition, Pro Forma Revenue			5,354,821
Business Acquisition, Pro Forma Net Income (Loss)			140,276
Business Acquisition, Pro Forma Earnings Per Share, Basic			$ 1.22
Business Acquisition, Pro Forma Earnings Per Share, Diluted			$ 1.19
Gain on bargain purchase	0	1,755			(667)	1,755
Gain on bargain purchase, net of taxes					410	1,078
Gain On Bargain Purchase Of Business Per Share Basic and Diluted						$ 0.01
Payments to Acquire Additional Interest in Subsidiaries	$ 2,526