Investments in Real Estate Partnerships - Schedule of Dispositions (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) property	Dec. 31, 2016 USD ($) property	Dec. 31, 2015 USD ($) property
Unconsolidated Properties [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from Sale of Equity Method Investments | $	$ 73,122	$ 174,090	$ 39,459
Equity Method Investment, Realized Gain (Loss) on Disposal | $	34,276	70,907	2,766
Equity Method Investment, Realized Gain (Loss) on Disposal, Parent Company's Share | $	$ 6,591	$ 25,003	$ 1,108
Operating Segments [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of Real Estate Properties Sold	6	11	5
Operating Segments [Member] | Unconsolidated Properties [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of Real Estate Properties Sold	3	10	2
Land [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of Real Estate Properties Sold	9	16	2
Land [Member] | Unconsolidated Properties [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of Real Estate Properties Sold	1	1	0