CONSOLIDATED STATEMENTS OF STOCKHOLDERS EQUITY (Parenthetical) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Common dividends declared, per share	$ 0.50	$ 0.60	$ 1.60	$ 1.87
7.875% Series A Cumulative Redeemable Preferred Stock [Member]
Preferred series dividends declared, per share	$ 0.492	$ 0.492	$ 1.477	$ 1.477
6.00% Series B Cumulative Convertible Preferred Stock [Member]
Preferred series dividends declared, per share	$ 0.000	$ 0.375	$ 0.375	$ 1.125
7.625% Series C Cumulative Redeemable Preferred Stock [Member]
Preferred series dividends declared, per share	$ 0.477		$ 0.715