Equity (Details Textuals) (USD $) Share data in Millions, except Per Share data, unless otherwise specified	1 Months Ended		3 Months Ended				9 Months Ended					3 Months Ended	9 Months Ended	3 Months Ended	9 Months Ended		12 Months Ended
	Apr. 30, 2011	Mar. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010	Mar. 18, 2011	Dec. 31, 2010	Feb. 28, 2009	Mar. 31, 2011 Maximum [Member]	Sep. 30, 2010 Maximum [Member]	Mar. 31, 2011 Minimum [Member]	Sep. 30, 2010 Minimum [Member]	Sep. 30, 2011 Class G Preferred Stock [Member]	Dec. 31, 2010 Class G Preferred Stock [Member]	Apr. 30, 2011 Underwritten Program [Member]
Class of Stock [Line Items]
Dividend per share																8.00%	8.00%
Cumulative redeemable preferred shares total redemption price																	$ 180,800,000
Dividend yield assumptions												3.20%	4.20%	3.00%	3.10%
Volatility assumptions					36.60%			78.30%
Sale of Stock [Line Items]
Net proceeds per common share of stock issued																		$ 13.71
Issuance of warrants, weighted average purchase price							Less than $6.00 per share
Equity (Textuals) [Abstract]
Number of common shares issued		10
Proceeds from issuance of common stock	130,200,000	60,000,000					129,792,000	440,472,000
Aggregate number of common shares to be issued as per Forward sale agreement	9.5
Cumulative redeemable preferred shares total redemption price per share	$ 25.105556
The per share amount of stock redeemed	$ 25.00
Redeemable preferred stock dividend per share prorated to redemption date	$ 0.105556
Write-off of original preferred share issuance costs				6,400,000			(6,402,000)
Dividend declared per common share			$ 0.06			$ 0.02	$ 0.14	$ 0.06
Increase to paid-in-capital							2,300,000
Number of common shares available for purchase through warrants											10.0
Issuance of warrants, exercise price per share		$ 6.00			$ 6.00						$ 6.00
Equity derivative liability - affiliate			$ 0				$ 0		$ 74,300,000	$ 96,237,000