Property Transactions Property Transactions (Held for Sale) (Details) $ in Thousands	1 Months Ended	3 Months Ended
	Nov. 01, 2016 USD ($)	Dec. 31, 2016 USD ($)	Mar. 31, 2016 USD ($)	Oct. 17, 2016 ft²	Sep. 30, 2016 USD ($) ft²	Dec. 31, 2015 USD ($) ft²
Long Lived Assets Held-for-sale [Line Items]
Real Estate Held for Sale, Accumulated Depreciation					$ 100,250	$ 7,072
Operating properties, net held for sale					$ 171,543	$ 6,421
Area of Real Estate Property | ft²					1,200,000	129,000
Sales of Real Estate			$ 22,000
Proceeds from Sale of Property Held-for-sale			$ 14,200
Restricted Cash and Cash Equivalents					$ 1,405	$ 0
Notes and accounts receivable held for sale					1,460	210
Deferred rents receivable held for sale					17,606	496
Intangible assets, net held for sale					11,721	119
Assets Held-for-sale, Not Part of Disposal Group					203,735	7,246
Notes payable held for sale					99,000	0
Accounts payable and accrued expenses held for sale					5,196	140
Intangible liabilities, net held for sale					638	0
Other liabilities held for sale					1,301	1,207
Liabilities held for sale					106,135	1,347
Intangible assets accumulated amortization, held for sale					19,420	128
Notes payable unamortized deferred loan costs, held for sale					188	0
Intangible liabilities accumulated amortization, held for sale					$ 794	$ 0
Subsequent Event [Member]
Long Lived Assets Held-for-sale [Line Items]
Area of Real Estate Property | ft²				941,000
Sales of Real Estate	$ 219,000	$ 268,000