Net Income Per Share (Schedule Of Net Income Per Share) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 29, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jul. 01, 2012	Apr. 01, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Earnings Per Share [Abstract]
Net Income	$ 11,432	$ 14,457	$ 13,985	$ 15,343	$ 16,079	$ 23,791	$ 21,522	$ 25,147	$ 55,217	$ 86,539	$ 91,368
Weighted average shares outstanding: Basic (in shares)									38,379,000	38,057,000	37,121,000
Weighted average shares outstanding: Dilutive potential common shares (in shares)									569,000	690,000	811,000
Weighted average shares outstanding: Total diluted shares (in shares)									38,948,000	38,747,000	37,932,000
Basic net income per share (in dollars per share)	$ 0.30	$ 0.37	$ 0.36	$ 0.40	$ 0.42	$ 0.62	$ 0.57	$ 0.67	$ 1.44	$ 2.27	$ 2.46
Diluted net income per share (in dollars per share)	$ 0.30	$ 0.37	$ 0.36	$ 0.39	$ 0.41	$ 0.61	$ 0.56	$ 0.65	$ 1.42	$ 2.23	$ 2.41
Anti-dilutive common stock options (in shares)									2,800,000	2,600,000	2,000,000