CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Unaudited) (Parenthetical) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Common dividends declared, per share	$ 0.65	$ 0.68	$ 1.27	$ 1.33
Series A Cumulative Redeemable Preferred Stock [Member]
Preferred series dividends declared, per share	$ 0.4922	$ 0.4922	$ 0.9844	$ 0.9844
Series B Cumulative Convertible Redeemable Preferred Stock [Member]
Preferred series dividends declared, per share	$ 0.375	$ 0.375	$ 0.75	$ 0.75