Impairment of Real Estate, Impairment of Unconsolidated Entities, Write-Off of Abandoned Development Projects and Gain (Loss) on Early Extinguishment of Debt (Details 1) (USD $)	3 Months Ended			6 Months Ended
	Oct. 31, 2011	Jul. 31, 2011	Jul. 31, 2010	Jul. 31, 2011	Jul. 31, 2010
Debt Instrument [Line Items]
Gain (loss) on early extinguishment of debt	$ 15,200,000	$ (5,471,000)	$ 1,896,000	$ (5,767,000)	$ 8,193,000
Summary of Company's impairment of unconsolidated entities
Total impairment of unconsolidated entities		0	2,282,000	0	15,181,000
Impairment of Real Estate, Impairment of Unconsolidated Entities, Write Off of Abandoned Development Projects And Gain On Early Extinguishment Of Debt (Textuals)
Write-off of abandoned development projects		5,088,000	37,000	5,245,000	37,000
Write-offs of abandoned development projects related to unconsolidated entities		0	2,557,000	0	2,557,000
Gain on early extinguishment of Urban Development Action Grant Loans				5,329,000
Gain on early extinguishment of nonrecourse mortgage debt				296,000
5.000% Convertible Senior Notes due 2016 [Member]
Debt Instrument [Line Items]
Gain (loss) on early extinguishment of debt		10,800,000
Mixed-Use Land Development [Member] | Mercy Campus at Central Station [Member]
Summary of Company's impairment of unconsolidated entities
Total impairment of unconsolidated entities		0	1,817,000	0	1,817,000
Mixed-Use Land Development [Member] | Old Stone Crossing at Caldwell Creek [Member]
Summary of Company's impairment of unconsolidated entities
Total impairment of unconsolidated entities		0		0	743,000
Office Buildings [Member] | 818 Mission Street [Member]
Summary of Company's impairment of unconsolidated entities
Total impairment of unconsolidated entities		0		0	4,018,000
Office Buildings [Member] | Bulletin Building [Member]
Summary of Company's impairment of unconsolidated entities
Total impairment of unconsolidated entities		0		0	3,543,000
Specialty Retail Centers [Member] | Metreon [Member]
Summary of Company's impairment of unconsolidated entities
Total impairment of unconsolidated entities		0		0	4,595,000
Other [Member]
Summary of Company's impairment of unconsolidated entities
Total impairment of unconsolidated entities		$ 0	$ 465,000	$ 0	$ 465,000