Cash and Cash Equivalents, Investments and Funds Held for Customers - Type of issue (Details) - USD ($) $ in Millions	Oct. 31, 2015	Jul. 31, 2015	Oct. 31, 2014	Jul. 31, 2014
Cash and Cash Equivalents Items [Line Items]
Cash and cash equivalents, Amortized Cost	$ 474	$ 808	$ 542	$ 849
Available-for-sale securities:
Total cash and cash equivalents, investments, and funds held for customers, Amortized Cost	849	2,062
Total cash and cash equivalents, investments, and funds held for customers, Fair Value	849	2,061
Total cash and cash equivalents
Cash and Cash Equivalents Items [Line Items]
Cash and cash equivalents, Amortized Cost	646	970
Cash and cash equivalents, Fair Value Disclosure	646	970
Municipal bonds
Available-for-sale securities:
Available-for-sale debt securities, Amortized Cost Basis	6	507
Available-for-sale securities, Fair Value Disclosure	6	506
Corporate notes
Available-for-sale securities:
Available-for-sale debt securities, Amortized Cost Basis	169	546
Available-for-sale securities, Fair Value Disclosure	169	546
U.S. agency securities
Available-for-sale securities:
Available-for-sale debt securities, Amortized Cost Basis	0	12
Available-for-sale securities, Fair Value Disclosure	0	12
Municipal auction rate securities
Available-for-sale securities:
Available-for-sale debt securities, Amortized Cost Basis	15	15
Available-for-sale securities, Fair Value Disclosure	15	15
Total available-for-sale debt securities
Available-for-sale securities:
Available-for-sale debt securities, Amortized Cost Basis	190	1,080
Available-for-sale securities, Fair Value Disclosure	190	1,079
Other long-term investments
Available-for-sale securities:
Other long-term investments	13	12
Available-for-sale securities, Fair Value Disclosure	$ 13	$ 12