Deferred Costs (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Components of Deferred Costs Net [Abstract]
Leasing Costs, Total Cost	$ 140,772	$ 123,724
Financing Costs, Total Cost	38,929	37,257
Total Cost	179,701	160,981
Leasing Costs, Accumulated Amortization	(50,990)	(43,930)
Financing Costs, Accumulated Amortization	(13,349)	(10,934)
Total, Accumulated Amortization	(64,339)	(54,864)
Leasing Costs, Deferred Costs, net	89,782	79,794
Financing Costs, Deferred Costs, net	25,580	26,323
Deferred Costs	$ 115,362	$ 106,117