Stockholders' Equity (Details 2) (USD $)	3 Months Ended		6 Months Ended		76 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Mar. 29, 2007
Reconciliation of the number of shares outstanding with the number of shares used in computing basic and diluted earnings per share
Common shares outstanding, end of period	37,257,000	37,163,000	37,257,000	37,163,000
Effect of using weighted average common shares outstanding	(67,000)	3,000	(129,000)	(52,000)
Shares used in computing earnings per share - basic	37,190,000	37,166,000	37,128,000	37,111,000
Effect of shares issuable under stock option plans based on the treasury stock method	121,000	81,000	107,000	92,000
Effect of contingently issuable restricted shares	54,000		114,000	29,000
Shares used in computing earnings per share - diluted	37,365,000	37,247,000	37,349,000	37,232,000
Number of shares of unvested contingently issuable restricted stock outstanding	100,000	200,000	100,000	200,000	100,000
Share Repurchase Program
Number of shares of outstanding common stock authorized to be acquired under a stock repurchase program	6,600,000		6,600,000		6,600,000	1,000,000
Maximum number of shares of common stock repurchased			100,000
Number of shares of common stock repurchased					5,900,000
Average price (in dollars per share)			$ 13.11		$ 10.95