Segment Information (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Jan. 31, 2013 segment	Jan. 31, 2012	Jan. 31, 2011
Financial data of six reportable segments
Number of reportable segments	6
Identifiable assets	$ 10,612,432	$ 10,504,283
Revenues from real estate operations	1,134,687	1,051,618	1,078,448
Operating expenses	732,275	654,346	632,822
Depreciation and amortization	229,661	208,801	225,082
Interest expense	269,229	249,799	298,201
Interest and other income	45,915	52,094	52,792
Capital expenditures	803,865	760,381	723,158
Commercial Group [Member]
Financial data of six reportable segments
Identifiable assets	7,127,228	7,326,286
Revenues from real estate operations	716,064	705,565	817,958
Operating expenses	388,412	357,671	386,497
Depreciation and amortization	165,393	155,848	171,200
Interest expense	185,175	174,364	220,093
Interest and other income	14,730	20,917	22,716
Capital expenditures	327,867	355,598	377,290
Commercial Group Land Sales [Member]
Financial data of six reportable segments
Revenues from real estate operations	45,999	54,363	24,742
Operating expenses	5,286	9,731	19,970
Residential Group [Member]
Financial data of six reportable segments
Identifiable assets	2,060,892	2,022,135
Revenues from real estate operations	269,637	245,701	202,366
Operating expenses	188,591	174,280	132,373
Depreciation and amortization	52,882	51,199	51,779
Interest expense	19,000	29,490	18,725
Interest and other income	21,155	19,816	19,829
Capital expenditures	149,160	154,475	222,712
Arena [Member]
Financial data of six reportable segments
Identifiable assets	980,321	643,783
Revenues from real estate operations	48,353	1,569	1,251
Operating expenses	49,175	12,536	8,302
Depreciation and amortization	8,888	0	0
Interest expense	(122)	(14,336)	(7,508)
Interest and other income	0	261	643
Capital expenditures	325,744	249,139	123,046
Land Development Group [Member]
Financial data of six reportable segments
Identifiable assets	246,873	352,248
Revenues from real estate operations	54,634	44,420	32,131
Operating expenses	48,361	47,543	38,650
Depreciation and amortization	840	240	334
Interest expense	3,801	3,443	3,007
Interest and other income	9,866	10,838	9,162
Capital expenditures	190	558	0
The Nets [Member]
Financial data of six reportable segments
Identifiable assets	1,111	(3,836)
Revenues from real estate operations	0	0	0
Operating expenses	0	0	0
Depreciation and amortization	0	0	0
Interest expense	0	0	0
Interest and other income	0	0	0
Capital expenditures	0	0	0
Corporate Activities [Member]
Financial data of six reportable segments
Identifiable assets	196,007	163,667
Revenues from real estate operations	0	0	0
Operating expenses	52,450	52,585	47,030
Depreciation and amortization	1,658	1,514	1,769
Interest expense	61,375	56,838	63,884
Interest and other income	164	262	442
Capital expenditures	$ 904	$ 611	$ 110