Accounting Policies (Details Textual 1) (USD $) In Millions, unless otherwise specified	Apr. 30, 2013
Variable Interest Entity [Line Items]
Maximum loss exposure for unconsolidated variable interest entities	$ 65
Collaterized borrowings of variable interest entity	$ 29
Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Number of variable interest entities	31
Number of properties representing variable interest entities	23
Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Number of variable interest entities	59