Investments in Real Estate Partnerships - Scheduled Principal Payments (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	$ 101,489
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal in Year Two	104,662
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal in Year Three	85,718
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal in Year Four	83,873
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal in Year Five	237,025
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal After Year Five	790,425
Unamortized debt premiums, net	(1,215)
Equity Method Investment, Summarized Financial Information, Notes Payable	1,401,977	$ 1,462,790
2016	47,609
2017	423,076
2018	62,461
2019	275,130
2020	237,997
Beyond 5 Years	820,601
Unamortized debt discounts (premiums)	5,604
Long-term Debt	1,872,478	$ 2,021,357
Scheduled Principal Payments [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	16,614
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal in Year Two	17,517
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal in Year Three	18,696
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal in Year Four	17,934
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal in Year Five	14,826
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal After Year Five	20,001
Unamortized debt premiums, net	0
Equity Method Investment, Summarized Financial Information, Notes Payable	105,588
2016	6,167
2017	5,778
2018	5,103
2019	4,130
2020	3,986
Beyond 5 Years	12,347
Unamortized debt discounts (premiums)	0
Long-term Debt	37,511
Mortgage Loan Maturities [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	84,875
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal in Year Two	77,385
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal in Year Three	67,022
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal in Year Four	65,939
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal in Year Five	222,199
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal After Year Five	770,424
Unamortized debt premiums, net	(1,215)
Equity Method Investment, Summarized Financial Information, Notes Payable	1,286,629
2016	41,442
2017	117,298
2018	57,358
2019	106,000
2020	84,011
Beyond 5 Years	58,254
Unamortized debt discounts (premiums)	9,302
Long-term Debt	473,665
Unsecured Maturities [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	0
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal in Year Two	9,760
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal in Year Three	0
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal in Year Four	0
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal in Year Five	0
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal After Year Five	0
Unamortized debt premiums, net	0
Equity Method Investment, Summarized Financial Information, Notes Payable	9,760
2016	0
2017	300,000
2018	0
2019	165,000
2020	150,000
Beyond 5 Years	750,000
Unamortized debt discounts (premiums)	(3,698)
Long-term Debt	1,361,302
Equity Method Investments [Member]
Schedule of Equity Method Investments [Line Items]
2016	37,238
2017	23,874
2018	27,655
2019	21,618
2020	85,506
Beyond 5 Years	295,357
Unamortized debt discounts (premiums)	(488)
Long-term Debt	$ 490,760