Fair Value Measurements - Recurring and Nonrecurring Basis (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in real estate partnerships	$ 442,927	$ 386,882
Provision for impairment	74,800	15,900	23,900
Fair Value, Measurements, Recurring [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Fair Value Disclosure	23,429	21,713
Interest Rate Derivative Assets, at Fair Value	4,307
Total	27,736
Derivative Liabilities	(76)	(37)
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	23,429	21,713
Interest Rate Derivative Assets, at Fair Value	0
Total	23,429
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	4,412
Total	4,412
Derivative Liabilities	(77)	(38)
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	(105)
Total	(105)
Derivative Liabilities	1	1
Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Provision for impairment	(54,500)	16,400
Equity Method Investment, Other than Temporary Impairment		(4,580)
Fair Value, Option, Changes in Fair Value, Gain (Loss)		(16,423)
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)		(11,843)
Fair Value, Measurements, Nonrecurring [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-Lived Assets	49,673	5,520
Investments in real estate partnerships		1,893
Assets, Fair Value Disclosure, Nonrecurring		7,413
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-Lived Assets	0	0
Investments in real estate partnerships		0
Assets, Fair Value Disclosure, Nonrecurring		0
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
Investments in real estate partnerships		0
Assets, Fair Value Disclosure, Nonrecurring		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	49,673	5,520
Investments in real estate partnerships		1,893
Assets, Fair Value Disclosure, Nonrecurring		$ 7,413