Short-term Borrowings and Long-term Debt (Details) $ in Billions	Jul. 31, 2019 USD ($)	Jul. 31, 2018 USD ($)
Line of Credit Facility [Line Items]
Number of Financial Institutions Committing to Lend Funds Under Lines of Credit	22
Line of Credit Facility, Maximum Borrowing Capacity	$ 15	$ 15
Five Year Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	5
364 Day Revolving Facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 10