Deferred Costs Deferred Costs (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Components of Deferred Costs Net [Abstract]
Leasing Costs, Total Cost	$ 147,528	$ 150,331
Financing Costs, Total Cost	40,205	40,246
Total Cost	187,733	190,577
Leasing Costs, Accumulated Amortization	(57,203)	(58,343)
Financing Costs, Accumulated Amortization	(11,152)	(9,991)
Total, Accumulated Amortization	68,355	68,334
Leasing, Deferred Costs, Net	90,325	91,988
Financing Costs, Deferred Costs, Net	29,053	30,255
Deferred Costs, Net	$ 119,378	$ 122,243