Segment Information (Details) (USD $)	3 Months Ended		6 Months Ended
	Jul. 31, 2013	Jul. 31, 2012	Jul. 31, 2013 segment unit	Jul. 31, 2012	Jan. 31, 2013
Financial data of six reportable segments
Number of strategic business units			3
Number of reportable operating segments			6
Number of reportable operating segments represented by the strategic business units			4
Identifiable assets	$ 10,728,101,000		$ 10,728,101,000		$ 10,612,432,000
Revenues from real estate operations	291,762,000	241,770,000	587,911,000	519,016,000
Operating expenses	191,404,000	163,612,000	393,527,000	320,483,000
Depreciation and amortization	91,857,000	50,897,000	160,232,000	100,261,000
Interest expense	91,723,000	59,354,000	177,974,000	114,244,000
Interest and other income	12,277,000	13,551,000	23,182,000	24,077,000
Capital expenditures	121,701,000	245,744,000	242,091,000	442,098,000
Commercial Group [Member]
Financial data of six reportable segments
Identifiable assets	6,778,113,000		6,778,113,000		7,127,228,000
Revenues from real estate operations	183,437,000	165,348,000	355,565,000	328,697,000
Operating expenses	99,104,000	90,767,000	194,265,000	172,283,000
Depreciation and amortization	68,866,000	38,965,000	113,406,000	75,981,000
Interest expense	53,920,000	42,676,000	106,755,000	82,677,000
Interest and other income	2,312,000	6,174,000	4,204,000	9,821,000
Capital expenditures	51,375,000	115,079,000	107,968,000	203,631,000
Commercial Group Land Sales [Member]
Financial data of six reportable segments
Revenues from real estate operations	791,000	49,000	26,391,000	40,049,000
Operating expenses	184,000	50,000	15,547,000	3,566,000
Residential Group [Member]
Financial data of six reportable segments
Identifiable assets	2,428,143,000		2,428,143,000		2,060,892,000
Revenues from real estate operations	63,545,000	63,679,000	127,342,000	125,304,000
Operating expenses	48,200,000	41,432,000	96,740,000	84,575,000
Depreciation and amortization	14,256,000	11,536,000	27,834,000	23,448,000
Interest expense	13,913,000	4,568,000	22,659,000	8,238,000
Interest and other income	6,399,000	4,835,000	12,546,000	9,309,000
Capital expenditures	52,353,000	27,648,000	101,222,000	53,585,000
Arena [Member]
Financial data of six reportable segments
Identifiable assets	974,618,000		974,618,000		980,321,000
Revenues from real estate operations	21,587,000	210,000	50,284,000	326,000
Operating expenses	15,533,000	6,469,000	39,484,000	10,757,000
Depreciation and amortization	7,871,000	0	17,276,000	0
Interest expense	9,349,000	(4,607,000)	18,362,000	(8,734,000)
Interest and other income	0	0	0	0
Capital expenditures	17,967,000	102,679,000	31,853,000	184,266,000
Land Development Group [Member]
Financial data of six reportable segments
Identifiable assets	277,753,000		277,753,000		246,873,000
Revenues from real estate operations	22,402,000	12,484,000	28,329,000	24,640,000
Operating expenses	15,692,000	11,271,000	21,385,000	22,948,000
Depreciation and amortization	102,000	139,000	200,000	246,000
Interest expense	(178,000)	2,475,000	(280,000)	4,226,000
Interest and other income	3,453,000	2,510,000	6,273,000	4,870,000
Capital expenditures	6,000	139,000	819,000	181,000
The Nets [Member]
Financial data of six reportable segments
Identifiable assets	0		0		1,111,000
Revenues from real estate operations	0	0	0	0
Operating expenses	0	0	0	0
Depreciation and amortization	0	0	0	0
Interest expense	0	0	0	0
Interest and other income	0	0	0	0
Capital expenditures	0	0	0	0
Corporate Activities [Member]
Financial data of six reportable segments
Identifiable assets	269,474,000		269,474,000		196,007,000
Revenues from real estate operations	0	0	0	0
Operating expenses	12,691,000	13,623,000	26,106,000	26,354,000
Depreciation and amortization	762,000	257,000	1,516,000	586,000
Interest expense	14,719,000	14,242,000	30,478,000	27,837,000
Interest and other income	113,000	32,000	159,000	77,000
Capital expenditures	$ 0	$ 199,000	$ 229,000	$ 435,000