Investments in Unconsolidated Entities (Details 1) (USD $)	3 Months Ended		6 Months Ended
	Jul. 31, 2011	Jul. 31, 2010	Jul. 31, 2011	Jul. 31, 2010	Jan. 31, 2011	Jan. 31, 2010
Real Estate
Completed rental properties	$ 7,101,431,000		$ 7,101,431,000		$ 8,215,425,000
Projects under construction and development	2,170,855,000		2,170,855,000		2,706,235,000
Land held for development or sale	263,224,000		263,224,000		244,879,000
Total Real Estate	9,535,510,000		9,535,510,000		11,166,539,000
Less accumulated depreciation	(1,501,353,000)		(1,501,353,000)		(1,614,399,000)
Real Estate, net	8,034,157,000		8,034,157,000		9,552,140,000
Cash and equivalents	412,348,000	186,728,000	412,348,000	186,728,000	193,372,000	251,405,000
Restricted cash - military housing bond funds	502,373,000		502,373,000		720,180,000
Other Assets	637,350,000		637,350,000		759,399,000
Total Assets	7,917,166,000		7,917,166,000		6,320,153,000
Mortgage debt and notes payable, nonrecourse	5,621,687,000		5,621,687,000		7,207,218,000
Members' and partners' equity	987,583,000		987,583,000		587,164,000
Total Liabilities and Members and Partners Equity	7,917,166,000		7,917,166,000		6,320,153,000
Operations:
Revenues	258,831,000	218,481,000	515,020,000	451,504,000
Operating expenses	(159,771,000)	(169,516,000)	(322,679,000)	(324,644,000)
Impairment of real estate	(235,000)	(1,100,000)	(5,070,000)	(1,100,000)
Depreciation and amortization - Real Estate Groups	(54,538,000)	(58,040,000)	(111,245,000)	(117,366,000)
Interest and other income	15,315,000	16,231,000	30,822,000	23,045,000
Net loss (pre-tax)	(11,117,000)	(9,967,000)	(28,181,000)	(16,293,000)
Company's portion of net earnings (loss) (pre-tax)	2,385,000	2,164,000	9,812,000	(2,852,000)
Impairment of investment in unconsolidated entities	0	(2,282,000)	0	(14,438,000)
Gain (loss) on disposition of equity method investments	0	(878,000)	12,567,000	(830,000)
Net earning (loss) (pre-tax) from unconsolidated entities	2,385,000	(996,000)	22,379,000	(18,120,000)
Equity Method Investee [Member]
Real Estate
Completed rental properties	6,905,798,000		6,905,798,000		5,514,041,000
Projects under construction and development	425,495,000		425,495,000		174,106,000
Land held for development or sale	230,431,000		230,431,000		272,930,000
Total Real Estate	7,561,724,000		7,561,724,000		5,961,077,000
Less accumulated depreciation	(1,158,399,000)		(1,158,399,000)		(944,968,000)
Real Estate, net	6,403,325,000		6,403,325,000		5,016,109,000
Cash and equivalents	125,605,000		125,605,000		109,246,000
Restricted cash - military housing bond funds	345,365,000		345,365,000		384,584,000
Other restricted cash and escrowed funds	292,490,000		292,490,000		206,778,000
Other Assets	750,381,000		750,381,000		536,246,000
Operating property assets held for sale	0		0		67,190,000
Mortgage debt and notes payable, nonrecourse	6,461,858,000		6,461,858,000		5,301,900,000
Other liabilities	467,725,000		467,725,000		369,871,000
Liabilities of operating property held for sale	0		0		61,218,000
Operations:
Operating expenses	(140,394,000)	(122,421,000)	(294,786,000)	(263,319,000)
Interest expense including early extinguishment of debt	(86,064,000)	(67,554,000)	(160,291,000)	(129,993,000)
Impairment of real estate				(1,457,000)
Depreciation and amortization - Real Estate Groups	(48,259,000)	(43,485,000)	(95,651,000)	(80,577,000)
Interest and other income	$ 4,769,000	$ 5,012,000	$ 7,527,000	$ 7,549,000