Impairment of Real Estate, Impairment of Unconsolidated Entities and Write-Off of Abandoned Development Projects(Detail Textuals) (USD $)	3 Months Ended		9 Months Ended
	Oct. 31, 2013	Oct. 31, 2012	Oct. 31, 2013	Oct. 31, 2012
Impairment of real estate impairment of unconsolidated entities and write off of abandoned development projects [Line Items]
Impairment of real estate	$ 200,155,000	$ 30,200,000	$ 208,210,000	$ 30,660,000
Impairment of unconsolidated entities	0	0	0	390,000
Write-off of abandoned development projects	26,540,000	370,000	29,317,000	14,029,000
LiveWork Las Vegas [Member]
Impairment of real estate impairment of unconsolidated entities and write off of abandoned development projects [Line Items]
Area of land parcel/project (in acres)	13.5		13.5
Impairment of real estate	112,838,000	0	112,838,000	0
Promenade Bolingbrook [Member]
Impairment of real estate impairment of unconsolidated entities and write off of abandoned development projects [Line Items]
Impairment of real estate	54,194,000	0	54,194,000	0
Orchard Town Center [Member]
Impairment of real estate impairment of unconsolidated entities and write off of abandoned development projects [Line Items]
Impairment of real estate	15,649,000	0	15,649,000	0
Building J at Illinois Science and Technology Park [Member]
Impairment of real estate impairment of unconsolidated entities and write off of abandoned development projects [Line Items]
Impairment of real estate	17,474,000	0	17,474,000	0
Brooklyn Atlantic Yards [Member]
Impairment of real estate impairment of unconsolidated entities and write off of abandoned development projects [Line Items]
Area of land parcel/project (in acres)	22		22
Halle Building [Member]
Impairment of real estate impairment of unconsolidated entities and write off of abandoned development projects [Line Items]
Impairment of real estate	0	30,200,000	0	30,200,000
Carrying value of real estate, fair value		10,500,000		10,500,000
Minimum [Member] | Brooklyn Atlantic Yards [Member]
Impairment of real estate impairment of unconsolidated entities and write off of abandoned development projects [Line Items]
Estimated future impairment charge			250,000,000
Maximum [Member] | Brooklyn Atlantic Yards [Member]
Impairment of real estate impairment of unconsolidated entities and write off of abandoned development projects [Line Items]
Estimated future impairment charge			350,000,000
Fair Value, Measurements, Nonrecurring [Member] | Comparable Property Market Analysis [Member]
Impairment of real estate impairment of unconsolidated entities and write off of abandoned development projects [Line Items]
Weighted average of input values impairment of real estate			$ 45