Mortgage Debt and Notes Payable, Nonrecourse (Details) (USD $) In Thousands, unless otherwise specified	Apr. 30, 2012
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 2013	$ 1,173,549
Mortgage debt and notes payable non recourse maturities including scheduled balloon payments in 2014	722,261
Mortgage debt and notes payable non recourse maturities including scheduled balloon payments in 2015	286,719
Mortgage debt and notes payable non recourse maturities including scheduled balloon payments in 2016	315,767
Mortgage debt and notes payable non recourse maturities including scheduled balloon payments in 2017	396,887
Mortgage debt and notes payable non recourse maturities including scheduled amortization in 2013	33,620
Mortgage debt and notes payable non recourse maturities including scheduled amortization in 2014	40,640
Mortgage debt and notes payable non recourse maturities including scheduled amortization in 2015	33,220
Mortgage debt and notes payable non recourse maturities including scheduled amortization in 2016	30,631
Mortgage debt and notes payable non recourse maturities including scheduled amortization in 2017	23,749
Mortgage debt and notes payable non recourse maturities including total maturities in 2013	1,207,169
Mortgage debt and notes payable non recourse maturities including total maturities in 2014	762,901
Mortgage debt and notes payable non recourse maturities including total maturities in 2015	319,939
Mortgage debt and notes payable non recourse maturities including total maturities in 2016	346,398
Mortgage debt and notes payable non recourse maturities including total maturities in 2017	420,636
Mortgage debt and notes payable non recourse maturities including total maturities thereafter	2,632,833
Total mortgage debt and notes payable, nonrecourse, including debt on held for divestiture properties	$ 5,689,876