Shareholders' Equity (Details) (USD $)	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2011 2000 Stock Buy Back Program [Member]	Dec. 31, 2011 2005 Rights Plan [Member]	Feb. 03, 2005 2005 Rights Plan [Member]	Dec. 31, 2011 2005 Rights Plan [Member] Individual Or Group [Member]	Dec. 31, 2011 2005 Rights Plan [Member] Institutional Investors [Member]
Schedule of Equity Method Investments [Line Items]
Maximum number of shares authorized for purchases under the program			500,000
Total shares purchased under the program	3,100,419	3,070,720	11,300
Number of rights awarded for each outstanding common share					1
Number of shares that each right entitles holder to purchase				0.0001
Purchase price per unit that share right entitles				$ 35
Minimum beneficial ownership percentage required to exercise the rights						10.00%	15.00%