Business Segments (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Summary information for the reportable segments
Rental and other property revenues (3)	$ 239,873		$ 236,546		$ 719,501		$ 700,734
Tax credit and asset management revenues	6,970		7,397		22,684		22,458
Total revenues	246,843		243,943		742,185		723,192
Property operating expenses (3)	95,174		93,898		288,816		282,064
Investment management expenses	1,279		373		3,552		3,503
Depreciation and amortization (3)	69,437		72,040		211,143		221,588
Provision for real estate impairment losses (3)	1,413		0		1,413		0
General and administrative expenses	10,665		10,962		31,322		33,894
Other expenses, net	1,408		2,158		7,397		6,281
Total operating expenses	179,376		179,431		543,643		547,330
Net operating income (loss)	67,467		64,512		198,542		175,862
Other items included in continuing operations	(49,281)		(57,537)		(150,373)		(168,071)
Income (loss) from continuing operations	18,186		6,975		48,169		7,791
Conventional Real Estate Operations [Member]
Summary information for the reportable segments
Rental and other property revenues (3)	195,965	[1]	181,691	[1]	573,171	[1]	537,639	[1]
Tax credit and asset management revenues
Total revenues	195,965		181,691		573,171		537,639
Property operating expenses (3)	67,646	[1]	63,071	[1]	198,977	[1]	188,812	[1]
Investment management expenses
Depreciation and amortization (3)		[1]		[1]		[1]
Provision for real estate impairment losses (3)		[1]				[1]
General and administrative expenses
Other expenses, net
Total operating expenses	67,646		63,071		198,977		188,812
Net operating income (loss)	128,319		118,620		374,194		348,827
Other items included in continuing operations
Income (loss) from continuing operations	128,319		118,620		374,194		348,827
Affordable Real Estate Operations [Member]
Summary information for the reportable segments
Rental and other property revenues (3)	23,728	[1]	23,238	[1]	70,731	[1]	69,660	[1]
Tax credit and asset management revenues
Total revenues	23,728		23,238		70,731		69,660
Property operating expenses (3)	9,278	[1]	9,379	[1]	29,143	[1]	28,302	[1]
Investment management expenses
Depreciation and amortization (3)		[1]		[1]		[1]
Provision for real estate impairment losses (3)		[1]				[1]
General and administrative expenses
Other expenses, net
Total operating expenses	9,278		9,379		29,143		28,302
Net operating income (loss)	14,450		13,859		41,588		41,358
Other items included in continuing operations
Income (loss) from continuing operations	14,450		13,859		41,588		41,358
Proportionate Adjustments [Member]
Summary information for the reportable segments
Rental and other property revenues (3)	8,148	[1],[2]	7,794	[1],[2]	24,110	[1],[2]	23,005	[1],[2]
Tax credit and asset management revenues		[2]		[2]		[2]		[2]
Total revenues	8,148	[2]	7,794	[2]	24,110	[2]	23,005	[2]
Property operating expenses (3)	2,822	[1],[2]	2,760	[1],[2]	7,915	[1],[2]	8,073	[1],[2]
Investment management expenses		[2]		[2]		[2]		[2]
Depreciation and amortization (3)		[1],[2]		[1],[2]		[1],[2]		[1],[2]
Provision for real estate impairment losses (3)		[1],[2]				[1],[2]
General and administrative expenses		[2]		[2]		[2]		[2]
Other expenses, net		[2]		[2]		[2]		[2]
Total operating expenses	2,822	[2]	2,760	[2]	7,915	[2]	8,073	[2]
Net operating income (loss)	5,326	[2]	5,034	[2]	16,195	[2]	14,932	[2]
Other items included in continuing operations		[2]		[2]		[2]		[2]
Income (loss) from continuing operations	5,326	[2]	5,034	[2]	16,195	[2]	14,932	[2]
Corporate and Other [Member]
Summary information for the reportable segments
Rental and other property revenues (3)	12,032	[1],[3]	23,823	[1],[3]	51,489	[1],[3]	70,430	[1],[3]
Tax credit and asset management revenues	6,970		7,397		22,684		22,458
Total revenues	19,002	[3]	31,220	[3]	74,173	[3]	92,888	[3]
Property operating expenses (3)	15,428	[1],[3]	18,688	[1],[3]	52,781	[1],[3]	56,877	[1],[3]
Investment management expenses	1,279		373		3,552		3,503
Depreciation and amortization (3)	69,437		72,040		211,143		221,588
Provision for real estate impairment losses (3)	1,413				1,413
General and administrative expenses	10,665		10,962		31,322		33,894
Other expenses, net	1,408		2,158		7,397		6,281
Total operating expenses	99,630	[3]	104,221	[3]	307,608	[3]	322,143	[3]
Net operating income (loss)	(80,628)	[3]	(73,001)	[3]	(233,435)	[3]	(229,255)	[3]
Other items included in continuing operations	(49,281)	[3]	(57,537)	[3]	(150,373)	[3]	(168,071)	[3]
Income (loss) from continuing operations	$ (129,909)	[3]	$ (130,538)	[3]	$ (383,808)	[3]	$ (397,326)	[3]

[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), depreciation and amortization and provision for real estate impairment losses. 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. As discussed in Note 3, effective January 1, 2014, we adopted ASU 2014-08, which revised the definition of a discontinued operation. In the segment presentation above, the current year and prior year operating results for apartment communities sold or classified as held for sale during 2014 are presented within the Corporate and Amounts Not Allocated to Segments column. The operating results for the three and nine months ended September 30, 2013, for apartment communities sold through December 31, 2013, are presented within discontinued operations and are accordingly excluded from the segment presentation above.