Investments in Real Estate Partnerships - Income Statment Summarized Financial Information (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Schedule of Equity Method Investments [Line Items]
Document Fiscal Year Focus	2013
Proceeds from sale of real estate investments	$ 212,632	$ 352,707	$ 86,233
Revenues and expenses for the investments in real estate partnerships on a combined basis
Total revenues	378,670	387,908	399,091
Operating expenses:
Depreciation and amortization	125,363	128,946	134,236
Operating and maintenance	55,423	55,394	62,442
General and administrative	7,385	7,549	7,905
Real estate taxes	45,451	46,395	49,103
Other expenses	1,725	3,521	3,477
Total operating expenses	235,347	241,805	257,163
Other expense (income):
Interest expense, net	95,505	104,694	112,099
Gain on sale of real estate	15,695	40,437	7,464
Loss (gain) on extinguishment of debt	(1,780)	967	(8,743)
Provision for impairment	0	3,775	0
Preferred return on equity investment	(4,499)	(2,211)	0
Other expense (income)	(1,258)	51	776
Total other expense	72,273	66,839	96,668
Net income (loss)	71,050	79,264	45,260
Income (Loss) from Equity Method Investments	31,718	23,807	9,643
Unconsolidated Properties [Member]
Schedule of Equity Method Investments [Line Items]
Proceeds from sale of real estate investments	145,295	119,275	43,710
Other expense (income):
Limited Liability Company (LLC) or Limited Partnership (LP), Managing Member or General Partner, Ownership Interest	100.00%	100.00%	100.00%
Gain on sale of real estate investments [Member]
Other expense (income):
Income (Loss) from Equity Method Investments	$ 3,847	$ 8,962	$ 2,114
Operating Segments [Member]
Other expense (income):
Number of Real Estate Properties Sold	12	20	8
Operating Segments [Member] | Unconsolidated Properties [Member]
Other expense (income):
Number of Real Estate Properties Sold	15	7	5
Land [Member]
Other expense (income):
Number of Real Estate Properties Sold	10	7	8
Land [Member] | Unconsolidated Properties [Member]
Other expense (income):
Number of Real Estate Properties Sold	3	1	1