Investments in Real Estate Partnerships - Scheduled Principal Payments (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Schedule of Equity Method Investments [Line Items]
2017	$ 91,618
2018	62,187
2019	125,205
2020	239,047
2021	288,970
Beyond 5 Years	840,067
Unamortized debt discounts (premiums)	(4,674)
Long-term Debt	1,642,420	$ 1,864,285
Mortgages [Member]
Schedule of Equity Method Investments [Line Items]
Long-term Debt	384,786	475,214
Mortgages [Member] \| Scheduled Principal Payments [Member]
Schedule of Equity Method Investments [Line Items]
2017	5,279
2018	4,829
2019	4,205
2020	4,636
2021	3,780
Beyond 5 Years	9,888
Unamortized debt discounts (premiums)	0
Long-term Debt	32,617
Mortgages [Member] \| Mortgage Loan Maturities [Member]
Schedule of Equity Method Investments [Line Items]
2017	86,339
2018	57,358
2019	106,000
2020	84,411
2021	35,190
Beyond 5 Years	65,179
Unamortized debt discounts (premiums)	4,662
Long-term Debt	439,139
Unsecured Debt [Member]
Schedule of Equity Method Investments [Line Items]
Long-term Debt	892,170	$ 1,190,403
Unsecured Debt [Member] \| Unsecured Maturities [Member]
Schedule of Equity Method Investments [Line Items]
2017	0
2018	0
2019	15,000
2020	150,000
2021	250,000
Beyond 5 Years	765,000
Unamortized debt discounts (premiums)	(9,336)
Long-term Debt	1,170,664
Unconsolidated Investments in Partnership [Member]
Schedule of Equity Method Investments [Line Items]
2017	37,430
2018	86,005
2019	84,170
2020	237,332
2021	222,106
Beyond 5 Years	653,080
Unamortized debt discounts (premiums)	(10,192)
Long-term Debt	1,309,931
Unconsolidated Investments in Partnership [Member] \| Mortgages [Member] \| Scheduled Principal Payments [Member]
Schedule of Equity Method Investments [Line Items]
2017	17,795
2018	18,983
2019	18,231
2020	15,133
2021	10,674
Beyond 5 Years	10,580
Unamortized debt discounts (premiums)	0
Long-term Debt	91,396
Unconsolidated Investments in Partnership [Member] \| Mortgages [Member] \| Mortgage Loan Maturities [Member]
Schedule of Equity Method Investments [Line Items]
2017	0
2018	67,022
2019	65,939
2020	222,199
2021	211,432
Beyond 5 Years	642,500
Unamortized debt discounts (premiums)	(10,192)
Long-term Debt	1,198,900
Unconsolidated Investments in Partnership [Member] \| Unsecured Debt [Member] \| Unsecured Maturities [Member]
Schedule of Equity Method Investments [Line Items]
2017	19,635
2018	0
2019	0
2020	0
2021	0
Beyond 5 Years	0
Unamortized debt discounts (premiums)	0
Long-term Debt	19,635
Unconsolidated Investments in Partnership, Pro-Rata Share [Member] [Member]
Schedule of Equity Method Investments [Line Items]
2017	10,505
2018	27,799
2019	21,766
2020	85,660
2021	82,806
Beyond 5 Years	243,982
Unamortized debt discounts (premiums)	(3,488)
Long-term Debt	$ 469,030

The amount of debt discount (net of debt premium) that was originally recognized at the issuance of the instrument that has yet to be amortized.

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