Fair Value Measurements - Recurring and Nonrecurring Basis (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Document Fiscal Year Focus	2016
Current Fiscal Year End Date	--12-31
Investments in real estate partnerships	$ 296,699	$ 306,206
Provision for impairment	1,700
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Fair Value Disclosure	28,588	29,093
Available-for-sale Securities	7,420	7,922
Interest Rate Cash Flow Hedge Asset at Fair Value	11,622
Total	47,630	37,015
Interest Rate Cash Flow Hedge Liability at Fair Value	(580)	(20,539)
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	28,588	29,093
Available-for-sale Securities	0	0
Interest Rate Cash Flow Hedge Asset at Fair Value	0
Total	28,588	29,093
Interest Rate Cash Flow Hedge Liability at Fair Value	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	7,420	7,922
Interest Rate Cash Flow Hedge Asset at Fair Value	11,622
Total	19,042	7,922
Interest Rate Cash Flow Hedge Liability at Fair Value	(580)	(20,539)
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	0
Interest Rate Cash Flow Hedge Asset at Fair Value	0
Total	0	0
Interest Rate Cash Flow Hedge Liability at Fair Value	$ 0	$ 0