Business Segments (Details) (USD $) In Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Summary information for the reportable segments
Rental and other property revenues	$ 269,525	$ 263,481	$ 805,749	$ 788,057
Asset management and tax credit revenues	11,885	9,711	28,772	24,208
Total revenues	281,410	273,192	834,521	812,265
Property operating expenses	119,903	116,786	356,634	362,784
Investment management expenses	2,386	2,609	7,604	10,979
Depreciation and amortization	97,321	101,704	287,739	305,066
Provision for operating real estate impairment losses	149		149
General and administrative expenses	12,664	12,096	36,162	39,015
Other expenses, net	4,870	4,416	13,952	2,173
Total operating expenses	237,293	237,611	702,240	720,017
Net operating income (loss)	44,117	35,581	132,281	92,248
Other items included in continuing operations	(70,428)	(82,573)	(232,831)	(213,541)
Income (loss) from continuing operations	(26,311)	(46,992)	(100,550)	(121,293)
Conventional [Member]
Summary information for the reportable segments
Rental and other property revenues	206,115	200,667	613,688	600,640
Total revenues	206,115	200,667	613,688	600,640
Property operating expenses	79,514	76,467	233,126	235,612
Total operating expenses	79,514	76,467	233,126	235,612
Net operating income (loss)	126,601	124,200	380,562	365,028
Income (loss) from continuing operations	126,601	124,200	380,562	365,028
Affordable [Member]
Summary information for the reportable segments
Rental and other property revenues	32,715	31,573	97,947	93,847
Total revenues	32,715	31,573	97,947	93,847
Property operating expenses	13,373	13,765	40,488	42,331
Total operating expenses	13,373	13,765	40,488	42,331
Net operating income (loss)	19,342	17,808	57,459	51,516
Income (loss) from continuing operations	19,342	17,808	57,459	51,516
Proportionate Adjustments [Member]
Summary information for the reportable segments
Rental and other property revenues	30,501	30,591	93,065	91,530
Total revenues	30,501	30,591	93,065	91,530
Property operating expenses	13,495	13,562	41,075	41,820
Total operating expenses	13,495	13,562	41,075	41,820
Net operating income (loss)	17,006	17,029	51,990	49,710
Income (loss) from continuing operations	17,006	17,029	51,990	49,710
Corporate and Amounts Not Allocated to Segments [Member]
Summary information for the reportable segments
Rental and other property revenues	194	650	1,049	2,040
Asset management and tax credit revenues	11,885	9,711	28,772	24,208
Total revenues	12,079	10,361	29,821	26,248
Property operating expenses	13,521	12,992	41,945	43,021
Investment management expenses	2,386	2,609	7,604	10,979
Depreciation and amortization	97,321	101,704	287,739	305,066
Provision for operating real estate impairment losses	149		149
General and administrative expenses	12,664	12,096	36,162	39,015
Other expenses, net	4,870	4,416	13,952	2,173
Total operating expenses	130,911	133,817	387,551	400,254
Net operating income (loss)	(118,832)	(123,456)	(357,730)	(374,006)
Other items included in continuing operations	(70,428)	(82,573)	(232,831)	(213,541)
Income (loss) from continuing operations	$ (189,260)	$ (206,029)	$ (590,561)	$ (587,547)