Preferred Stock (Details) (USD $)	1 Months Ended		12 Months Ended				1 Months Ended	12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2011 Series C Preferred Stock [Member]	Oct. 31, 2006 Series C Depositary Share [Member]	Dec. 31, 2011 Series C Depositary Share [Member]	Oct. 02, 2006 Series C Depositary Share [Member]
Class of Stock [Line Items]
Preferred Stock, Dividend Rate, Percentage						7.375%		7.375%
Preferred Stock, Shares Issued				3,680,000					3,680,000
Ratio of Depositary Share to Underlying Preferred Stock									0.01
Proceeds from Issuance of Preferred Stock							$ 92,000,000
Stock Issuance Costs	$ 9,060,000	$ 10,393,000	$ (19,453,000)	$ (1,000)	$ (113,000)		$ 3,098,000
Preferred Stock, Liquidation Preference Per Share	$ 25.00		$ 25.00	$ 25.00				$ 25.00
Preferred Stock, Fixed Annual Dividend Per Share, Depository Shares								$ 1.84375
Preferred Stock, Redemption Price Per Share						$ 2,500.00		$ 25.00