Business Segments (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2016	Mar. 31, 2015
Summary information for the reportable segments
Rental and other property revenues (3)		$ 241,481	$ 238,289
Tax credit and asset management revenues		4,758	5,976
Total revenues		246,239	244,265
Property operating expenses (3)		88,397	95,492
Investment management expenses		975	1,603
Depreciation and amortization		79,828	74,432
General and administrative expenses		11,935	10,652
Other expenses, net		1,570	1,019
Total operating expenses		182,705	183,198
Net operating income (loss)		63,534	61,067
Other items included in income before gain on dispositions (4)		(39,836)	(42,610)
Income before gain on dispositions		23,698	18,457
Operating Segments [Member] | Conventional Real Estate Operations [Member]
Summary information for the reportable segments
Rental and other property revenues (3)	[1]	207,729	194,204
Total revenues		207,729	194,204
Property operating expenses (3)	[1]	67,446	66,283
Total operating expenses		67,446	66,283
Net operating income (loss)		140,283	127,921
Income before gain on dispositions		140,283	127,921
Operating Segments [Member] | Affordable Real Estate Operations [Member]
Summary information for the reportable segments
Rental and other property revenues (3)	[1]	24,910	24,232
Total revenues		24,910	24,232
Property operating expenses (3)	[1]	10,070	10,230
Total operating expenses		10,070	10,230
Net operating income (loss)		14,840	14,002
Income before gain on dispositions		14,840	14,002
Proportionate Adjustments [Member]
Summary information for the reportable segments
Rental and other property revenues (3)	[2]	8,822	8,397
Total revenues	[2]	8,822	8,397
Property operating expenses (3)	[2]	2,907	3,604
Total operating expenses	[2]	2,907	3,604
Net operating income (loss)	[2]	5,915	4,793
Income before gain on dispositions	[2]	5,915	4,793
Corporate Nonsegment And Other Reconciling Items Member [Member]
Summary information for the reportable segments
Rental and other property revenues (3)	[3]	20	11,456
Tax credit and asset management revenues	[3]	4,758	5,976
Total revenues	[3]	4,778	17,432
Property operating expenses (3)	[3]	7,974	15,375
Investment management expenses	[3]	975	1,603
Depreciation and amortization	[3]	79,828	74,432	[1]
General and administrative expenses	[3]	11,935	10,652
Other expenses, net	[3]	1,570	1,019
Total operating expenses	[3]	102,282	103,081
Net operating income (loss)	[3]	(97,504)	(85,649)
Other items included in income before gain on dispositions (4)	[3],[4]	(39,836)	(42,610)
Income before gain on dispositions	[3]	$ (137,340)	$ (128,259)

[1] Proportionate property net operating income, our key measurement of segment profit or loss excludes property management revenues (which are included in rental and other property revenues), property management expenses and casualty gains and losses (which are included in property operating expenses) and depreciation and amortization. Accordingly, we do not allocate these amounts to our segments.

[2] Represents adjustments for the noncontrolling interests in consolidated real estate partnerships’ share of the results of our consolidated apartment communities and the results of consolidated apartment communities that we do not manage, which are excluded from our measurement of segment performance but included in the related consolidated amounts, and our share of the results of operations of our unconsolidated real estate partnerships that we manage, which are included in our measurement of segment performance but excluded from the related consolidated amounts.

[3] Our basis for assessing segment performance excludes the results of apartment communities sold or classified as held for sale. In the segment presentation above, the current year and prior year operating results for apartment communities sold or classified as held for sale during 2016 or 2015 are presented within the Corporate and Amounts Not Allocated to Segments column. Proportionate property net operating income, our key measurement of segment profit or loss, also excludes property management expenses and casualty gains and losses (which are included in property operating expenses) and depreciation and amortization. Accordingly, we do not allocate these amounts to our segments and they are presented within the Corporate and Amounts Not Allocated to Segments column.

[4] Other items included in income before gain on dispositions primarily consist of interest expense and income tax benefit.