Common Stock (Common Stock Repurchase Program) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended				156 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2011 Repurchase of Equity	Dec. 31, 2011 Repurchase of Equity		Mar. 21, 2011 Repurchase of Equity		Dec. 31, 2010 Repurchase of Equity
Repurchase of Equity [Line Items]
Shares repurchased				2,782,455	25,406,184	[1]
Cost, including commission	$ 87,008	$ 33,726	$ 24,105	$ 86,508	$ 423,647	[1]
2010 Plan balance at December 31, 2010									676,271
2011 Plan repurchase shares authorized							2,500,000	[2]
Total remaining shares available for repurchase at December 31, 2011				393,816	393,816

[1] Represents repurchased shares and cost since inception of the stock repurchase program in 1999.

[2] On March 21, 2011, the Board of Directors authorized an additional repurchase of the Company’s common stock (the “2011 Plan”).