Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2013
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized	100,000,000	100,000,000
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	500,000,000	500,000,000
Common stock, issued	85,920,290	85,402,408
Common stock, outstanding	85,920,290	85,402,408
Series A preferred shares
Preferred stock, shares authorized	2,000,000	2,000,000
Preferred stock, shares issued	2,000,000	2,000,000
Preferred stock, shares outstanding	2,000,000	2,000,000
Preferred stock, aggregate liquidation preference (in dollars)	$ 50,385	$ 50,398
Preferred stock, dividend rate (as a percent)	9.25%	9.25%
Series B preferred shares
Preferred stock, shares authorized	3,000,000	3,000,000
Preferred stock, shares issued	3,000,000	3,000,000
Preferred stock, shares outstanding	3,000,000	3,000,000
Preferred stock, aggregate liquidation preference (in dollars)	75,492	75,324
Preferred stock, dividend rate (as a percent)	7.875%	7.875%
Series C preferred shares
Preferred stock, shares authorized	3,400,000	3,400,000
Preferred stock, shares issued	3,400,000	3,400,000
Preferred stock, shares outstanding	3,400,000	3,400,000
Preferred stock, aggregate liquidation preference (in dollars)	$ 85,505	$ 85,522
Preferred stock, dividend rate (as a percent)	7.125%	7.125%