Treasury Stock (Details) (USD $)	1 Months Ended	6 Months Ended
	May 31, 2008	Jul. 01, 2012	Dec. 31, 2011
Treasury Stock (Textual) [Abstract]
Common stock held in treasury		$ 306,227,000	$ 300,584,000
Common stock held in treasury, shares		21,296,593	20,724,106
Approximate shares available for future issuances		7,500,000
Shares repurchased under Board of Directors authorized program	1,000,000
Shares repurchased		572,487
Shares repurchased under Board of Directors authorized program, value		$ 5,600,000
Shares repurchased under Board of Directors authorized program, per share	$ 13	$ 9.86