Consolidated Balance Sheets (Parenthetical) (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2012	Dec. 31, 2011
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, authorized	20,000,000	20,000,000
Common stock, par value	$ 0.01	$ 0.01
Common stock, authorized	100,000,000	100,000,000
Common stock, shares issued	53,654,000	53,002,000
Common stock, shares outstanding	53,654,000	52,988,000
Common stock in treasury, shares	100,000	113,000
8 1/2% Series A Cumulative Redeemable Shares [Member]
Preferred stock, dividend rate percentage	8.50%	8.50%
Preferred stock, liquidation preference	$ 50	$ 50
Preferred stock, shares issued	868,000	868,000
Preferred stock, shares outstanding	868,000	868,000