Property Dispositions, Discontinued Operations and Real Estate Impairment - Additional Information (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2016 USD ($)	Mar. 31, 2015 USD ($) Property
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Debt satisfaction gains (charges), net	$ (162)	$ 10,375
Other asset impairment charges		1,139
Mortgages [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Debt extinguishment amount		30,293
Sold Properties [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Aggregate gross disposition price	58,225	4,950
Gain on sale of properties	17,015	1,725
Transferred Property [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Debt satisfaction gains (charges), net	(162)	$ 10,466
Office Building [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Real estate number of properties transferred | Property		2
Office Building [Member] | Transferred Property [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Aggregate gross disposition price	$ 400