Business Segments (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Summary information for the reportable segments
Rental and other property revenues	$ 265,728	$ 254,803
Asset management and tax credit revenues	8,071	9,236
Total revenues	273,799	264,039
Property operating expenses	108,642	115,347
Investment management expenses	3,388	2,976
Depreciation and amortization	94,317	93,967
Provision for real estate impairment losses	6,364
General and administrative expenses	11,624	11,181
Other expenses, net	6,269	3,897
Total operating expenses	230,604	227,368
Net operating income (loss)	43,195	36,671
Other items included in continuing operations	(67,419)	68,342
Income (loss) from continuing operations	(24,224)	(31,671)
Conventional Real Estate Operations [Member]
Summary information for the reportable segments
Rental and other property revenues	208,328	200,793
Total revenues	208,328	200,793
Property operating expenses	76,499	76,448
Total operating expenses	76,499	76,448
Net operating income (loss)	131,829	124,345
Income (loss) from continuing operations	131,829	124,345
Affordable Real Estate Operations [Member]
Summary information for the reportable segments
Rental and other property revenues	30,922	30,037
Total revenues	30,922	30,037
Property operating expenses	12,994	12,426
Total operating expenses	12,994	12,426
Net operating income (loss)	17,928	17,611
Income (loss) from continuing operations	17,928	17,611
Proportionate Adjustments [Member]
Summary information for the reportable segments
Rental and other property revenues	26,341	23,394
Total revenues	26,341	23,394
Property operating expenses	10,023	10,554
Total operating expenses	10,023	10,554
Net operating income (loss)	16,318	12,840
Income (loss) from continuing operations	16,318	12,840
Corporate and Amounts Not Allocated to Segments [Member]
Summary information for the reportable segments
Rental and other property revenues	137	579
Asset management and tax credit revenues	8,071	9,236
Total revenues	8,208	9,815
Property operating expenses	9,126	15,919
Investment management expenses	3,388	2,976
Depreciation and amortization	94,317	93,967
Provision for real estate impairment losses	6,364
General and administrative expenses	11,624	11,181
Other expenses, net	6,269	3,897
Total operating expenses	131,088	127,940
Net operating income (loss)	(122,880)	(118,125)
Other items included in continuing operations	(67,419)	68,342
Income (loss) from continuing operations	$ (190,299)	$ (186,467)