Impairment of Real Estate, Impairment of Unconsolidated Entities and Write-Off of Abandoned Development Projects (Details 2) (Fair Value, Measurements, Nonrecurring [Member], USD $)	9 Months Ended
	Oct. 31, 2013		Oct. 31, 2012
Indicative bids [Member]
Non-recurring Impairment of Real Estate Including Discontiued Operations
Fair value of impairment of real estate	$ 212,204,000		$ 83,193,000
Fair value valuation technique	Indicative Bids		Indicative Bids
Fair value unobservable input	Indicative Bids		Indicative Bids
Fair value range of input values	N/A	[1]	N/A	[1]
Comparable Property Market Analysis [Member]
Non-recurring Impairment of Real Estate Including Discontiued Operations
Fair value of impairment of real estate	29,500,000
Fair value valuation technique	Comparable Property Market Analysis
Fair value unobservable input	Price Per Square Foot
Discounted cash flow [Member]
Non-recurring Impairment of Real Estate Including Discontiued Operations
Fair value of impairment of real estate			10,500,000
Fair value valuation technique			Discounted Cash Flow
Fair value unobservable input			Discount Rate
Percentage of input values impairment of real estate			10.00%
Minimum [Member] | Comparable Property Market Analysis [Member]
Non-recurring Impairment of Real Estate Including Discontiued Operations
Range of input values impairment of real estate	22
Maximum [Member] | Comparable Property Market Analysis [Member]
Non-recurring Impairment of Real Estate Including Discontiued Operations
Range of input values impairment of real estate	$ 55

[1] These fair value measurements were derived from bona fide purchase offers from third party prospective buyers, subject to the Company’s corroboration for reasonableness.