Condensed Consolidated Balance Sheets (Parenthetical) (USD $)	Jun. 30, 2011	Dec. 31, 2010
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	100,000,000	100,000,000
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	400,000,000	400,000,000
Common stock, shares issued	45,700,399	45,685,678
Common stock, shares outstanding	45,700,399	45,685,678
Class A [Member]
Preferred stock, shares authorized	3,300,000	3,300,000
Preferred stock, cumulative dividend per share	$ 0.40	$ 0.40
Preferred stock, shares issued	587,101	598,772
Preferred stock, shares outstanding	587,101	598,772
Class B [Member]
Preferred stock, shares authorized	300,000	300,000
Preferred stock, cumulative dividend per share	$ 0.50	$ 0.50
Preferred stock, shares issued	77,500	77,500
Preferred stock, shares outstanding	77,500	77,500