Computation of Earnings Per Share (Details) (USD $)	3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended
	Sep. 28, 2012	Sep. 30, 2011	Sep. 28, 2012	Sep. 30, 2011	Sep. 28, 2012 Equity awards granted to employees [Member]	Sep. 30, 2011 Equity awards granted to employees [Member]	Sep. 28, 2012 Equity awards granted to employees [Member]	Sep. 30, 2011 Equity awards granted to employees [Member]	Sep. 28, 2012 Warrant [Member]	Sep. 30, 2011 Warrant [Member]	Sep. 28, 2012 Warrant [Member]	Sep. 30, 2011 Warrant [Member]	Nov. 30, 2010 Convertible Debt [Member] Convertible Debt Securities [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net earnings	$ 14,982,000	$ 12,965,000	$ 40,864,000	$ 41,184,000
Weighted Average Number of Shares Outstanding, Basic	26,455,000	26,339,000	26,380,000	26,250,000
Earnings Per Share, Basic	$ 0.57	$ 0.49	$ 1.55	$ 1.57
Incremental Common Shares Attributable to Share-based Payment Arrangements	168,000	222,000	160,000	238,000
Weighted average shares issuable on exercise of convertible notes	0	0	0	42,000
Weighted Average Number of Shares Outstanding, Diluted	26,623,000	26,561,000	26,540,000	26,530,000
Earnings Per Share, Diluted	$ 0.56	$ 0.49	$ 1.54	$ 1.55
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount					336,893	165,482	351,103	233,965	3,397,902	3,386,739	3,395,861	3,386,739
Convertible Notes, Face Amount													$ 115,000,000