Income Taxes (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jul. 02, 2011	Jun. 30, 2012	Jul. 02, 2011	Dec. 31, 2011	Dec. 31, 2010
Income Tax Contingency [Line Items]
Change in other uncertain tax benefits			$ (1,344,000)	$ 1,846,000
Unrecognized tax benefits	71,855,000	73,369,000	71,855,000	73,369,000	73,199,000	71,523,000
Expected change in unrecognized tax benefits in the next twelve months	(5,000,000)		(5,000,000)
Income Taxes (Details) [Abstract]
Effective income tax rate	14.50%	14.00%	14.80%	15.00%
U. K. Tax Contingency [Member]
Income Tax Contingency [Line Items]
Reversal of interest on unrecognized tax benefits		$ 2,000,000		$ 2,000,000
Percentage point change in effective tax rate		(1.4)		(0.7)