Preferred Stock, Common Stock and Dividends (Details) (USD $)	1 Months Ended					3 Months Ended		6 Months Ended
	May 31, 2011	Apr. 30, 2011	Feb. 28, 2011	Mar. 31, 2010	Apr. 30, 2009	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010	Aug. 15, 2011	Aug. 02, 2011	Dec. 31, 2010	Mar. 10, 2010	Apr. 07, 2009	Dec. 23, 2008
Preferred Stock, Common Stock and Dividends
Series A cumulative perpetual preferred shares, issued (in shares)						216,000		216,000				216,000
Series A Cumulative perpetual preferred shares, par value (in dollars per share)						$ 0.01		$ 0.01				$ 0.01
Series A Cumulative perpetual preferred shares, per share liquidation value (in dollars per share)						$ 1,000		$ 1,000				$ 1,000
Series A cumulative perpetual preferred shares, aggregate liquidation value						$ 216,000,000		$ 216,000,000
Senior preferred stock, dividend rate for first five years (as a percent)								5.00%
Senior preferred stock, dividend rate thereafter (as a percent)								9.00%
Warrants to purchase entity's common stock (in shares)						1,326,238		1,326,238
Warrants, exercise price (in dollars per share)						$ 24.43		$ 24.43
Percentage of aggregate common stock investment on exercise of warrant to Senior Preferred Stock investment (as a percent)								15.00%
Warrants, term (in years)								10
Senior preferred stock, dividend paid	2,700,000		2,700,000
Senior preferred stock, future payment										2,700,000
Series A cumulative perpetual preferred shares, fair value as if issued on a stand-alone basis						130,900,000		130,900,000
Warrants, fair value as if issued on a stand-alone basis						8,000,000		8,000,000
Series A Cumulative perpetual preferred shares, discount						6,712,000		6,712,000				7,932,000			12,400,000
Period of amortization of discount on preferred shares (in years)								5
Amortization of discount on series A cumulative perpetual preferred shares						615,000	577,000	1,220,000	1,145,000
Cash dividends paid to common shareholders (in dollars per share)		$ 0.19
Semi annual cash dividend payable, maximum (in dollars per share)					$ 0.33
Repurchase of common stock, authorized amount				40,000,000	40,000,000
Period of repurchase of common stock (in months)													12	12
Cumulative number of shares repurchased under all stock repurchase programs (in shares)											7,501,455
Cumulative cost of shares repurchased under all stock repurchase programs											$ 232,336,000