Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data	Sep. 30, 2011	Dec. 31, 2010
Assets:
Intangible lease assets, accumulated amortization	$ 118,574	$ 125,193
Tenant receivables, allowance for doubtful accounts	809	1,298
Deferred financing costs, accumulated amortization	8,611	11,740
Deferred lease costs, accumulated amortization	115,633	111,671
Liabilities:
Intangible lease liabilities, accumulated amortization	65,496	60,850
Stockholders' Equity:
Shares-in-trust, shares authorized (in shares)	150,000,000	150,000,000
Shares-in-trust, shares outstanding (in shares)	0	0
Preferred stock, par value (in dollars per share)	$ 0	$ 0
Preferred stock, shares authorized (in shares)	100,000,000	100,000,000
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	750,000,000	750,000,000
Common stock, shares outstanding (in shares)	172,826,991	172,658,489
Building and Building Improvements [Member]
Assets:
Real Estate Investment Property, Accumulated Depreciation	$ 766,163	$ 707,314