Investments in Real Estate Partnerships - Income Statment Summarized Financial Information (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($) property	Dec. 31, 2015 USD ($) property	Dec. 31, 2014 USD ($) property
Schedule of Equity Method Investments [Line Items]
Document Fiscal Year Focus	2016
Revenues and expenses for the investments in real estate partnerships on a combined basis
Total revenues	$ 364,087	$ 363,745	$ 361,103
Operating expenses:
Depreciation and amortization	99,252	111,648	117,780
Operating and maintenance	52,725	51,970	55,216
General and administrative	5,342	5,292	5,503
Real estate taxes	42,813	43,769	42,380
Other expenses	2,356	2,989	2,234
Total operating expenses	202,488	215,668	223,113
Other expense (income):
Interest expense, net	69,193	79,477	84,155
Equity Method Investment, Summarized Financial Information, Gain Loss on Sale of Real Estate	70,907	2,766	28,856
Loss (gain) on extinguishment of debt	69	0	114
Provision for impairment	0	9,102	2,123
Other expense (income)	2,197	1,516	988
Total other expense	552	87,329	58,524
Net income (loss)	161,047	60,748	79,466
Unconsolidated Properties [Member]
Schedule of Equity Method Investments [Line Items]
Proceeds from sale of real estate investments	174,090	39,459	88,106
Other expense (income):
Income (Loss) from Equity Method Investments	70,907	2,766	28,856
Equity Method Investment, Amount Sold	$ 25,003	$ 1,108	$ 13,615
Operating Segments [Member]
Other expense (income):
Number of Real Estate Properties Sold | property	11	5	11
Operating Segments [Member] | Unconsolidated Properties [Member]
Other expense (income):
Number of Real Estate Properties Sold | property	10	2	6
Land [Member]
Other expense (income):
Number of Real Estate Properties Sold | property	16	2	6
Land [Member] | Unconsolidated Properties [Member]
Other expense (income):
Number of Real Estate Properties Sold | property	1	0	2