Segment Information (Details) (USD $) In Thousands	3 Months Ended		6 Months Ended
	Jul. 31, 2011	Jul. 31, 2010	Jul. 31, 2011	Jul. 31, 2010	Jan. 31, 2011
Financial data of five reportable segments
Total assets	$ 10,666,179		$ 10,666,179		$ 12,059,701
Capital Expenditure	192,882	173,354	360,580	400,085
Revenues from real estate operations	253,205	294,221	561,629	563,003
Operating expenses	159,771	169,516	322,679	324,644
Depreciation and amortization	54,538	58,040	111,245	117,366
Interest expense	64,064	84,795	130,979	165,977
Interest and other income	15,315	16,231	30,822	23,045
Commercial Group [Member]
Financial data of five reportable segments
Total assets	7,864,524		7,864,524		8,617,287
Capital Expenditure	151,872	121,414	266,497	282,720
Revenues from real estate operations	186,418	221,255	386,996	430,588
Operating expenses	98,787	108,436	199,145	209,402
Depreciation and amortization	40,380	44,847	83,229	91,250
Interest expense	41,459	59,924	87,417	118,078
Interest and other income	7,714	8,264	14,455	10,209
Residential Group [Member]
Financial data of five reportable segments
Total assets	1,982,305		1,982,305		2,825,527
Capital Expenditure	40,523	51,924	93,563	117,349
Revenues from real estate operations	57,525	53,790	111,029	105,182
Operating expenses	40,359	33,321	76,536	65,152
Depreciation and amortization	13,748	12,654	27,193	25,032
Interest expense	9,040	9,167	15,254	14,023
Interest and other income	4,998	5,668	10,874	8,237
Land Development Group [Member]
Financial data of five reportable segments
Total assets	497,737		497,737		498,190
Capital Expenditure	337		350
Revenues from real estate operations	7,862	5,618	15,952	12,476
Operating expenses	10,193	7,423	19,418	17,871
Depreciation and amortization	54	100	114	199
Interest expense	776	25	1,600	1,333
Interest and other income	2,553	2,231	5,394	4,425
The Nets [Member]
Financial data of five reportable segments
Total assets	4,614		4,614
Capital Expenditure
Revenues from real estate operations
Operating expenses
Depreciation and amortization
Interest expense
Interest and other income
Corporate Activities [Member]
Financial data of five reportable segments
Total assets	316,999		316,999		118,697
Capital Expenditure	150	16	170	16
Operating expenses	9,798	9,430	24,425	20,436
Depreciation and amortization	356	439	709	885
Interest expense	12,789	15,679	26,708	32,543
Interest and other income	50	68	99	174
Commercial Group Land Sales [Member]
Financial data of five reportable segments
Revenues from real estate operations	1,400	13,558	47,652	14,757
Operating expenses	$ 634	$ 10,906	$ 3,155	$ 11,783