Investments in Real Estate Partnerships - Income Statment Summarized Financial Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenues and expenses for the investments in real estate partnerships on a combined basis
Total revenues	$ 417,053	$ 414,631	$ 396,596
Operating expenses:
Depreciation and amortization	97,844	99,847	99,327
Operating and maintenance	65,811	66,299	58,283
General and administrative	6,201	5,697	5,582
Real estate taxes	53,410	54,119	49,904
Other operating expenses	2,709	2,700	4,574
Total operating expenses	225,975	228,662	217,670
Other expense (income):
Interest expense, net	75,449	73,508	73,244
Equity Method Investment, Summarized Financial Information, Gain Loss on Sale of Real Estate	(64,798)	(16,624)	(34,276)
Provision for impairment, net of tax	9,223	0	0
Total other expense (income)	19,874	56,884	38,968
Net income (loss)	171,204	129,085	139,958
Unconsolidated Properties [Member]
Other expense (income):
Income (Loss) from Equity Method Investments	$ 60,956	$ 42,974	$ 43,341