Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Assets:
Intangible lease assets, accumulated amortization	$ 79,640	$ 119,419
Tenant receivables, allowance for doubtful accounts	346	631
Deferred financing costs, accumulated amortization	9,887	9,214
Deferred lease costs, accumulated amortization	115,640	120,358
Liabilities:
Intangible lease liabilities, accumulated amortization	39,451	63,981
Stockholders' Equity:
Shares-in-trust, shares authorized	150,000,000	150,000,000
Shares-in-trust, shares outstanding	0	0
Preferred stock, par value (in dollars per share)	$ 0	$ 0
Preferred stock, shares authorized	100,000,000	100,000,000
Preferred stock, shares outstanding	0	0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	750,000,000	750,000,000
Common stock, shares issued	168,044,328	172,629,748
Common stock, shares outstanding	168,044,328	172,629,748
Building and Building Improvements [Member]
Assets:
Buildings and improvements, accumulated depreciation	$ 857,993	$ 792,342