Mortgage Debt and Notes Payable, Nonrecourse (Details) (USD $) In Thousands	Jul. 31, 2011	Jan. 31, 2011
Composition of mortgage debt and notes payable, nonrecourse maturities including scheduled amortization and balloon payment
Mortgage debt and notes payable non recourse maturities including scheduled balloon payments in 2012	$ 417,843
Mortgage debt and notes payable non recourse maturities including scheduled balloon payments in 2013	959,517
Mortgage debt and notes payable non recourse maturities including scheduled balloon payments in 2014	834,295
Mortgage debt and notes payable non recourse maturities including scheduled balloon payments in 2015	378,507
Mortgage debt and notes payable non recourse maturities including scheduled balloon payments in 2016	328,148
Mortgage debt and notes payable non recourse maturities including scheduled amortization in 2012	54,239
Mortgage debt and notes payable non recourse maturities including scheduled amortization in 2013	96,348
Mortgage debt and notes payable non recourse maturities including scheduled amortization in 2014	41,241
Mortgage debt and notes payable non recourse maturities including scheduled amortization in 2015	31,951
Mortgage debt and notes payable non recourse maturities including scheduled amortization in 2016	29,306
Mortgage debt and notes payable non recourse maturities including total maturities in 2012	472,082
Mortgage debt and notes payable non recourse maturities including total maturities in 2013	1,055,865
Mortgage debt and notes payable non recourse maturities including total maturities in 2014	875,536
Mortgage debt and notes payable non recourse maturities including total maturities in 2015	410,458
Mortgage debt and notes payable non recourse maturities including total maturities in 2016	357,454
Mortgage debt and notes payable non recourse maturities including total maturities thereafter	2,450,292
Mortgage debt and notes payable, nonrecourse	$ 5,621,687	$ 7,207,218