Business Segments (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Summary information for the reportable segments
Rental and other property revenues		$ 238,637	$ 239,492	$ 476,926	$ 479,628
Tax credit and asset management revenues		6,146	6,926	12,122	15,714
Total revenues		244,783	246,418	489,048	495,342
Property operating expenses		87,930	94,500	183,422	193,768
Investment management expenses		1,086	1,021	2,689	2,273
Depreciation and amortization		75,150	71,399	149,582	141,706
General and administrative expenses		12,062	10,119	22,714	20,646
Other expenses, net		2,912	3,582	3,931	5,874
Total operating expenses		179,140	180,621	362,338	364,267
Net operating income (loss)		65,643	65,797	126,710	131,075
Other items included in continuing operations		(41,736)	(47,854)	(84,346)	(101,092)
Income from continuing operations		23,907	17,943	42,364	29,983
Operating Segments [Member] | Conventional Real Estate Operations [Member]
Summary information for the reportable segments
Rental and other property revenues		201,437	182,934	398,678	362,199
Total revenues		201,437	182,934	398,678	362,199
Property operating expenses		65,700	62,153	133,209	125,018
Total operating expenses		65,700	62,153	133,209	125,018
Net operating income (loss)		135,737	120,781	265,469	237,181
Income from continuing operations		135,737	120,781	265,469	237,181
Operating Segments [Member] | Affordable Real Estate Operations [Member]
Summary information for the reportable segments
Rental and other property revenues		24,158	23,613	48,391	46,993
Total revenues		24,158	23,613	48,391	46,993
Property operating expenses		9,103	9,589	19,333	19,856
Total operating expenses		9,103	9,589	19,333	19,856
Net operating income (loss)		15,055	14,024	29,058	27,137
Income from continuing operations		15,055	14,024	29,058	27,137
Proportionate Adjustments [Member]
Summary information for the reportable segments
Rental and other property revenues	[1]	9,320	7,225	18,049	14,362
Total revenues	[1]	9,320	7,225	18,049	14,362
Property operating expenses	[1]	3,237	1,942	6,843	4,395
Total operating expenses	[1]	3,237	1,942	6,843	4,395
Net operating income (loss)	[1]	6,083	5,283	11,206	9,967
Income from continuing operations	[1]	6,083	5,283	11,206	9,967
Corporate Nonsegment And Other Reconciling Items Member [Member]
Summary information for the reportable segments
Rental and other property revenues	[2]	3,722	25,720	11,808	56,074
Tax credit and asset management revenues	[2]	6,146	6,926	12,122	15,714
Total revenues	[2]	9,868	32,646	23,930	71,788
Property operating expenses	[2]	9,890	20,816	24,037	44,499
Investment management expenses	[2]	1,086	1,021	2,689	2,273
Depreciation and amortization	[2]	75,150	71,399	149,582	141,706
General and administrative expenses	[2]	12,062	10,119	22,714	20,646
Other expenses, net	[2]	2,912	3,582	3,931	5,874
Total operating expenses	[2]	101,100	106,937	202,953	214,998
Net operating income (loss)	[2]	(91,232)	(74,291)	(179,023)	(143,210)
Other items included in continuing operations	[2]	(41,736)	(47,854)	(84,346)	(101,092)
Income from continuing operations	[2]	$ (132,968)	$ (122,145)	$ (263,369)	$ (244,302)

[1] 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.

[2] 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 2015 or 2014 are presented within the Corporate and Amounts Not Allocated to Segments column.