Land held for divestiture (Details Textuals) (USD $)	3 Months Ended			6 Months Ended
	Jul. 31, 2013	Jul. 31, 2012	Apr. 30, 2012	Jul. 31, 2013	Jul. 31, 2012	Jan. 31, 2013
Land held for divestiture [Line Items]
Ownership percentage of land development opportunity			100.00%
Carrying value of land held for divestiture	$ 1,990,000			$ 1,990,000		$ 2,706,000
Bad debts expense	9,000,000	0		9,000,000	0
Impairment of land held for divestiture	0	15,796,000		0	15,796,000
North Carolina land [Member]
Land held for divestiture [Line Items]
Area of Land Parcel Sold in 2006 (in acres)	1,000			1,000
Estimated fair value of the underlying collateral	4,100,000			4,100,000
Bad debts expense	9,000,000			9,000,000
Bad debt expense, net of noncontrolling interests	8,300,000			8,300,000
Bad debt expense, after tax	4,980,000			4,980,000
Prosper, Texas [Member]
Land held for divestiture [Line Items]
Ownership percentage of land development opportunity		51.00%			51.00%
Sales Price of Land		29,800,000			29,800,000
Gain on sale of land held for divestiture		7,600,000			7,600,000
Gain loss on sale of land net of noncontrolling interest		3,900,000			3,900,000
Central Station [Member]
Land held for divestiture [Line Items]
Impairment of land held for divestiture		17,000,000			17,000,000
Unsolicited offer to purchase ownership interest in remaining land parcels		30,000,000
Mesa del Sol [Member]
Land held for divestiture [Line Items]
Impairment of land held for divestiture		$ 15,000,000			$ 15,000,000
Acres of land held for divestiture (in acres)		3,000			3,000