Fair Value Measurements - Recurring and Nonrecurring Basis (Details)	12 Months Ended
	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($) property
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Document Fiscal Year Focus	2015
Current Fiscal Year End Date	--12-31
Investments in real estate partnerships	$ 306,206,000	$ 333,167,000
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Fair Value Disclosure	29,093,000	28,134,000
Available-for-sale Securities	7,922,000
Total	37,015,000
Derivative Liabilities	(20,539,000)	(18,794,000)
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	29,093,000	28,134,000
Available-for-sale Securities	0
Total	29,093,000
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
Available-for-sale Securities	7,922,000
Total	7,922,000
Derivative Liabilities	(20,539,000)	(18,794,000)
Derivative Liability, Fair Value, Gross Liability	20,539,000	18,794,000
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
Available-for-sale Securities	0
Total	0
Derivative Liabilities	0	0
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)	$ 0	$ (175,000)
Land [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of impaired land parcels | property		2