Condensed Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Receivables allowance	$ 1,759	$ 2,822
Accrued rental income allowance	3,086	3,181
Debt costs accumulated amortization	13,637	20,213
Unamortized premium - mortgages payable	214	130
Unamortized discount - notes payable	$ 10,599	$ 10,816
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)	15,000,000	15,000,000
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	375,000,000	375,000,000
Common stock, shares issued (in shares)	126,421,631	121,991,677
Common stock, shares outstanding (in shares)	126,421,631	121,991,677
Excess stock, par value (in dollars per share)	$ 0.01	$ 0.01
Excess stock, shares authorized (in shares)	390,000,000	390,000,000
Excess stock, shares issued (in shares)	0	0
Excess stock, shares outstanding (in shares)	0	0
Series D Depositary Share
Series D and E, depositary shares issued (in shares)	11,500,000	11,500,000
Series D and E, depositary shares outstanding (in shares)	11,500,000	11,500,000
Series D and E, stated liquidation value per share (in dollars per share)	$ 25	$ 25
Series E Depositary Share
Series D and E, depositary shares issued (in shares)	11,500,000	11,500,000
Series D and E, depositary shares outstanding (in shares)	11,500,000	11,500,000
Series D and E, stated liquidation value per share (in dollars per share)	$ 25	$ 25