Investments in Real Estate Partnerships - Income Statment Summarized Financial Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Schedule of Equity Method Investments [Line Items]
Document Fiscal Year Focus	2018
Revenues and expenses for the investments in real estate partnerships on a combined basis
Total revenues	$ 414,631	$ 396,596	$ 364,087
Operating expenses:
Depreciation and amortization	99,847	99,327	99,252
Operating and maintenance	66,299	58,283	52,725
General and administrative	5,697	5,582	5,342
Real estate taxes	54,119	49,904	42,813
Other expenses	1,003	2,923	2,356
Total operating expenses	226,965	216,019	202,488
Other expense (income):
Interest expense, net	73,508	73,244	69,193
Equity Method Investment, Summarized Financial Information, Gain Loss on Sale of Real Estate	16,624	34,276	70,907
Loss (gain) on extinguishment of debt	0	0	69
Other expense (income)	1,697	1,651	2,197
Total other expense	58,581	40,619	552
Net income (loss)	129,085	139,958	161,047
Unconsolidated Properties [Member]
Other expense (income):
Income (Loss) from Equity Method Investments	$ 16,624	$ 34,276	$ 70,907