Stockholders' Equity and Noncontrolling Interests (Details) - USD ($) $ / shares in Units, $ in Thousands, shares in Millions			1 Months Ended	3 Months Ended		9 Months Ended
	Nov. 12, 2014	Feb. 12, 2013	Dec. 31, 2014	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Class of Stock [Line Items]
Income attributable to noncontrolling interests				$ 2,617	$ 2,374	$ 7,628	$ 9,231
6.875 Series C Cumulative Redeemable Preferred Stock
Class of Stock [Line Items]
Number of depositary shares sold		5.6
Depository shares to cumulative redeemable preferred stock ratio		1.00%
Percentage of redeemable preferred stock		6.875%
Cash proceeds from sale depositary shares		$ 135,200
Dividend payment accrual date		Feb. 12, 2018
Cumulative redeemable preferred stock liquidation preference (in usd per share)		$ 25.00
Annual dividend on depositary shares (in usd per share)		$ 1.71875
Series C Cumulative Redeemable Preferred Stock
Class of Stock [Line Items]
Number of depositary shares sold	1.6
Percentage of redeemable preferred stock		6.875%
Cash proceeds from sale depositary shares	$ 39,300
Series A Cumulative Redeemable Preferred Stock
Class of Stock [Line Items]
Dividend rate on preferred stock			8.00%