Discontinued Operations Discontinued Operations (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011 property
Long Lived Assets Held-for-sale [Line Items]
Number of Real Estate Properties Held-for-Sale		2
Real estate assets and other assets held for sale, net	$ 0	$ 84,156
Deferred rent receivables, net	115,418	101,142
Deferred leasing costs and acquisition-related intangible assets, net	189,968	155,522
Accounts payable, accrued expenses and other liabilities	154,734	81,713
Deferred revenue and acquisition-related intangible liabilities, net	117,904	79,781
Rents received in advance and tenant security deposits	37,654	26,917
Liabilities and deferred revenue of real estate assets held for sale	0	13,286
Assets Held-for-sale [Member]
Long Lived Assets Held-for-sale [Line Items]
Real estate assets and other assets held for sale, net		84,156
Deferred rent receivables, net		6,749
Deferred leasing costs and acquisition-related intangible assets, net		2,375
Accounts payable, accrued expenses and other liabilities		24
Deferred revenue and acquisition-related intangible liabilities, net		13,223
Rents received in advance and tenant security deposits		39
Liabilities and deferred revenue of real estate assets held for sale		13,286
Land and Land Improvements [Member]
Long Lived Assets Held-for-sale [Line Items]
Real estate assets held for sale		6,490
Building and Building Improvements [Member]
Long Lived Assets Held-for-sale [Line Items]
Real estate assets held for sale		83,447
Real Estate [Member]
Long Lived Assets Held-for-sale [Line Items]
Real estate assets held for sale		89,937
Accumulated depreciation		(14,905)
Real estate assets and other assets held for sale, net		$ 75,032