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Fair Value Measurements - Recurring and Nonrecurring Basis (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Document Fiscal Year Focus	2014
Current Fiscal Year End Date	--12-31
Investments in real estate partnerships	$ 333,167	$ 358,849
Provision for impairment	1,257us-gaap_ImpairmentOfRealEstate	6,000us-gaap_ImpairmentOfRealEstate	74,816us-gaap_ImpairmentOfRealEstate
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	28,134	61,918
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Fair Value Disclosure	28,134	26,681
Interest Rate Derivative Assets, at Fair Value	0	0
Total	28,134	26,681
Derivative Liabilities	0	0
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Fair Value Disclosure	0	0
Interest Rate Derivative Assets, at Fair Value	0	35,237
Total	0	35,237
Derivative Liabilities	18,794	34
Derivative Liability, Fair Value, Gross Liability	(18,794)	(34)
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Fair Value Disclosure	0	0
Interest Rate Derivative Assets, at Fair Value	0	0
Total	0	0
Derivative Liabilities	0	0
Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-Lived Assets	397	4,686
Fair Value, Measurements, Nonrecurring [Member] \| Long Lived Assets Held And Used [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Option, Changes in Fair Value, Gain (Loss)	(175)	(6,000)
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
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Fair Value, Measurements, Nonrecurring [Member] \| Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-Lived Assets	0	0
Fair Value, Measurements, Nonrecurring [Member] \| Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-Lived Assets	$ 397	$ 4,686
Minimum [Member]
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Fair Value Inputs, Long-term Revenue Growth Rate		0.00%
Fair Value Inputs, Discount Rate		9.00%
Minimum [Member] \| Overall Cap Rate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Inputs, Cap Rate		8.00%
Minimum [Member] \| Terminal Cap Rate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Inputs, Cap Rate		8.50%
Land [Member]
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Number of impaired land parcels	2