Consolidated Balance Sheets (Parenthetical) (USD $)	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012 8.034% Series A Cumulative Redeemable Perpetual Preferred Stock	Dec. 31, 2011 8.034% Series A Cumulative Redeemable Perpetual Preferred Stock	Dec. 31, 2012 Cumulative Series C Six Point Seven Five Percent Redeemable Perpetual Preferred Stock [Member]	Dec. 31, 2011 Cumulative Series C Six Point Seven Five Percent Redeemable Perpetual Preferred Stock [Member]
Cumulative Redeemable Preferred Stock, par value	$ 0.01	$ 0.01
Cumulative Redeemable Preferred Stock, shares authorized	0	8,000,000
Cumulative Redeemable Preferred Stock, shares issued	0	8,000,000
Cumulative Redeemable Preferred Stock, shares outstanding	0	8,000,000
Preferred stock, par value	$ 0.01	$ 0.01	$ 0.01	$ 0.01	$ 0.01	$ 0.01
Preferred Stock, Shares Authorized	9,945,542	2,000,000	0	0	54,461	0
Preferred stock, shares issued	0	0	0	0	54,458	0
Preferred stock, shares outstanding	0	0	0	0	54,458	0
Common Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	41,596,655	41,078,200
Common stock, shares outstanding	41,596,655	41,078,200