Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2015	Dec. 31, 2014
Capital stock, total shares authorized	850,000,000	850,000,000
Capital stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Capital stock, shares of excess common stock	238,000,000	238,000,000
Capital stock, authorized shares of preferred stock	100,000,000	100,000,000
Preferred stock stated dividend rate percentage	8.375%	8.375%
Series J 8 3/8% cumulative redeemable preferred stock, shares authorized	1,000,000	1,000,000
Series J 8 3/8% cumulative redeemable preferred stock, shares issued	796,948	796,948
Series J 8 3/8% cumulative redeemable preferred stock, shares outstanding	796,948	796,948
Series J 8 3/8% cumulative redeemable preferred stock, liquidation value (in dollars)	$ 39,847	$ 39,847
Common stock held in treasury, shares	5,397,729	3,540,754
Common stock
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized	511,990,000	511,990,000
Common stock, shares issued	314,807,366	314,320,664
Common stock, shares outstanding	314,807,366	314,320,664
Class B common stock
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized	10,000	10,000
Common stock, shares issued	8,000	8,000
Common stock, shares outstanding	8,000	8,000