Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) (USD $)	Jun. 30, 2011
Common stock, par value (in dollars per share)	$ 0.0001
Common stock, shares authorized (in shares)	649,702,178
Common stock, shares issued (in shares)	32,724,235
Common stock, shares outstanding (in shares)	31,324,808
4.875% Series G Cumulative Convertible Preferred Stock [Member]
Cumulative convertible preferred stock, par value (in dollars per share)	$ 0.0001
Cumulative convertible preferred stock, shares issued (in shares)	5,980,000
Cumulative convertible preferred stock, shares outstanding (in shares)	178,249
7.125% Series H Cumulative Redeemable Preferred Stock [Member]
Cumulative redeemable preferred stock, par value (in dollars per share)	$ 0.0001
Cumulative redeemable preferred stock, shares authorized (in shares)	2,950,000
Cumulative redeemable preferred stock, shares issued (in shares)	2,950,000
Cumulative redeemable preferred stock, shares outstanding (in shares)	2,950,000
7.8125% Series F Cumulative Redeemable Preferred Stock [Member]
Cumulative redeemable preferred stock, par value (in dollars per share)	$ 0.0001
Cumulative redeemable preferred stock, shares authorized (in shares)	1,000,000
Cumulative redeemable preferred stock, shares issued (in shares)	1,000,000
Cumulative redeemable preferred stock, shares outstanding (in shares)	1,000,000