Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Tenant and other receivables, allowance for doubtful accounts	$ 1,625	$ 1,636
Accrued rental income, allowance	3,448	3,636
Unsecured senior notes, discount	13,710	14,146
Unsecured exchangeable senior notes, discount	$ 0	$ 182
Excess stock, par value	$ 0.01	$ 0.01
Excess stock, shares authorized	150,000,000	150,000,000
Excess stock, shares issued	0	0
Excess stock, shares outstanding	0	0
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	50,000,000	50,000,000
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	250,000,000	250,000,000
Common stock, shares issued	153,096,211	153,062,001
Common stock, shares outstanding	153,017,311	152,983,101
Treasury common stock at cost, shares	78,900	78,900
Series B Cumulative Redeemable Preferred Stock [Member]
Preferred stock, par value	$ 0.01	$ 0
Preferred stock, shares authorized	92,000	92,000
Series B Dividend Rate Percentage	5.25%	0.00%
Series B, Liquidation Preference Per Share	$ 2,500.00	$ 2,500.00
Series B, shares issued	80,000	80,000
Series B, Shares Outstanding	80,000	80,000