Investments in Real Estate Partnerships - Scheduled Principal Payments (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	$ 86,996
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal in Year Two	120,132
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal in Year Three	322,626
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal in Year Four	105,164
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal in Year Five	55,888
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal After Year Five	830,152
Unamortized debt premiums, net	(1,015)
Equity Method Investment, Summarized Financial Information, Notes Payable	1,519,943	1,816,648
2013	172,632
2014	418,182
2015	102,148
2016	489,693
2017	61,514
Beyond 5 Years	607,303
Unamortized debt discounts (premiums)	3,225
Long-term Debt	1,854,697	1,941,891
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	19,921
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal in Year Two	20,382
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal in Year Three	17,550
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal in Year Four	17,685
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal in Year Five	18,888
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal After Year Five	54,158
Unamortized debt premiums, net	0
Equity Method Investment, Summarized Financial Information, Notes Payable	148,584
2013	7,094
2014	5,747
2015	5,487
2016	4,881
2017	4,156
Beyond 5 Years	17,005
Unamortized debt discounts (premiums)	0
Long-term Debt	44,370
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	53,015
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal in Year Two	99,750
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal in Year Three	305,076
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal in Year Four	87,479
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal in Year Five	37,000
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal After Year Five	775,994
Unamortized debt premiums, net	(1,015)
Equity Method Investment, Summarized Financial Information, Notes Payable	1,357,299
2013	15,538
2014	62,435
2015	21,661
2016	84,812
2017	57,358
Beyond 5 Years	190,298
Unamortized debt discounts (premiums)	4,873
Long-term Debt	436,975
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	14,060
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal in Year Two	0
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	14,060
2013	150,000
2014	350,000
2015	75,000
2016	400,000
2017	0
Beyond 5 Years	400,000
Unamortized debt discounts (premiums)	(1,648)
Long-term Debt	1,373,352
Equity Method Investments [Member]
Schedule of Equity Method Investments [Line Items]
Notes payable (note 8)	534,100	597,400
2013	25,460
2014	43,107
2015	113,362
2016	27,053
2017	15,723
Beyond 5 Years	310,014
Unamortized debt discounts (premiums)	(579)
Long-term Debt	$ 534,140