Investments in Real Estate Partnerships - Income Statment Summarized Financial Information (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Revenues and expenses for the investments in real estate partnerships on a combined basis
Total revenues	$ 387,908	$ 399,091	$ 437,029
Operating expenses:
Depreciation and amortization	128,946	134,236	155,146
Operating and maintenance	55,394	62,442	67,541
General and administrative	7,549	7,905	7,383
Real estate taxes	46,395	49,103	55,926
Other expenses	3,521	3,477	3,666
Total operating expenses	241,805	257,163	289,662
Other expense (income):
Interest expense, net	104,694	112,099	129,581
Gain on sale of real estate	(40,437)	(7,464)	(8,976)
Loss (gain) on extinguishment of debt	967	(8,743)	0
Loss on hedge ineffectiveness	51	0	0
Provision for impairment	3,775	0	78,908
Preferred return on equity investment	(2,211)	0	0
Other expense (income)	0	776	(383)
Total other expense	66,839	96,668	199,130
Net income (loss)	79,264	45,260	(51,763)
Income (Loss) from Equity Method Investments	$ 23,807	$ 9,643	$ (12,884)