Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Apr. 30, 2012	Apr. 30, 2011	Jan. 31, 2012
Financial data of five reportable segments
Identifiable assets	$ 10,531,236		$ 10,504,283
Revenues from real estate operations	296,652	304,180
Operating expenses	166,851	160,689
Depreciation and amortization	52,833	55,853
Interest expense	58,516	66,181
Interest and other income	10,679	15,507
Capital Expenditure	196,354	167,698
Commercial Group [Member]
Financial data of five reportable segments
Identifiable assets	7,983,068		7,970,069
Revenues from real estate operations	179,191	196,334
Operating expenses	93,988	97,539
Depreciation and amortization	39,534	41,995
Interest expense	38,822	45,224
Interest and other income	3,799	6,741
Capital Expenditure	170,139	114,625
Residential Group [Member]
Financial data of five reportable segments
Identifiable assets	2,021,987		2,022,135
Revenues from real estate operations	65,305	53,504
Operating expenses	44,939	36,777
Depreciation and amortization	12,863	13,445
Interest expense	4,348	6,214
Interest and other income	4,475	5,876
Capital Expenditure	25,937	53,040
Land Development Group [Member]
Financial data of five reportable segments
Identifiable assets	363,015		352,248
Revenues from real estate operations	12,156	8,090
Operating expenses	11,677	9,225
Depreciation and amortization	107	60
Interest expense	1,751	824
Interest and other income	2,360	2,841
Capital Expenditure	42	13
The Nets [Member]
Financial data of five reportable segments
Identifiable assets	(5,794)		(3,836)
Revenues from real estate operations
Operating expenses
Depreciation and amortization
Interest expense
Interest and other income
Capital Expenditure
Corporate Activities [Member]
Financial data of five reportable segments
Identifiable assets	168,960		163,667
Revenues from real estate operations
Operating expenses	12,731	14,627
Depreciation and amortization	329	353
Interest expense	13,595	13,919
Interest and other income	45	49
Capital Expenditure	236	20
Commercial Group Land Sales [Member]
Financial data of five reportable segments
Revenues from real estate operations	40,000	46,252
Operating expenses	$ 3,516	$ 2,521