Cash and Cash Equivalents, Investments and Funds Held for Customers (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended	12 Months Ended
	Apr. 30, 2011	Jul. 31, 2010	Jan. 31, 2011	Apr. 30, 2010	Jan. 31, 2010	Jul. 31, 2009
Classification On Balance Sheets Abstract
Cash and cash equivalents	$ 1,369	$ 214	$ 433	$ 430	$ 337	$ 679
Investments	459	1,408
Funds held for customers	383	337
Long-term investments	81	91
Available-for-sale debt securities:
Total available-for-sale debt securities, amortized cost	709	1,643
Total available-for-sale debt securities, fair value	711	1,645
Available-for-sale debt securities classified by the stated maturity date of the security
Due within one year, amortized cost	283	432
Due within one year, fair value	283	433
Due within two years, amortized cost	182	365
Due within two years, fair value	183	366
Due within three years, amortized cost	109	164
Due within three years, fair value	110	164
Due after three years, amortized cost	135	682
Due after three years, fair value	135	682
Total available-for-sale debt securities, amortized cost	709	1,643
Total available-for-sale debt securities, fair value	711	1,645
Cash and Cash Equivalents, Investments and Funds Held for Customers (Textuals)
Number of available-for-sale debt securities	52
Fair value below amortized cost for available for sale debt securities.	0.4
Municipal auction rate securities	77	87
Available-for-sale debt securities with an interest reset date, put date or mandatory call date, percentage	83.00%	89.00%
Mandatory call date	Within two years	Within two years
Cost [Member]
Classification On Balance Sheets Abstract
Cash and cash equivalents	1,369	214
Investments	458	1,407
Funds held for customers	382	336
Long-term investments	81	91
Total cash and cash equivalents, investments and funds held for customers	2,290	2,048
Type of issue:
Total cash and cash equivalents	1,577	401
Available-for-sale debt securities:
Other long-term investments	4	4
Total cash and cash equivalents, investments and funds held for customers	2,290	2,048
Fair Value [Member]
Classification On Balance Sheets Abstract
Cash and cash equivalents	1,369	214
Investments	459	1,408
Funds held for customers	383	337
Long-term investments	81	91
Total cash and cash equivalents, investments and funds held for customers	2,292	2,050
Type of issue:
Total cash and cash equivalents	1,577	401
Available-for-sale debt securities:
Other long-term investments	4	4
Total cash and cash equivalents, investments and funds held for customers	2,292	2,050
Municipal bonds [Member]
Available-for-sale debt securities:
Total available-for-sale debt securities, amortized cost	357	1,049
Total available-for-sale debt securities, fair value	357	1,050
Available-for-sale debt securities classified by the stated maturity date of the security
Total available-for-sale debt securities, amortized cost	357	1,049
Total available-for-sale debt securities, fair value	357	1,050
Municipal auction rate securities [Member]
Available-for-sale debt securities:
Total available-for-sale debt securities, amortized cost	77	87
Total available-for-sale debt securities, fair value	77	87
Available-for-sale debt securities classified by the stated maturity date of the security
Total available-for-sale debt securities, amortized cost	77	87
Total available-for-sale debt securities, fair value	77	87
Corporate notes [Member]
Available-for-sale debt securities:
Total available-for-sale debt securities, amortized cost	199	333
Total available-for-sale debt securities, fair value	200	334
Available-for-sale debt securities classified by the stated maturity date of the security
Total available-for-sale debt securities, amortized cost	199	333
Total available-for-sale debt securities, fair value	200	334
U.S. agency securities [Member]
Available-for-sale debt securities:
Total available-for-sale debt securities, amortized cost	76	174
Total available-for-sale debt securities, fair value	77	174
Available-for-sale debt securities classified by the stated maturity date of the security
Total available-for-sale debt securities, amortized cost	76	174
Total available-for-sale debt securities, fair value	77	174
Available-for-Sale Debt Securities [Member]
Available-for-sale debt securities:
Total available-for-sale debt securities, amortized cost	709	1,643
Total available-for-sale debt securities, fair value	711	1,645
Available-for-sale debt securities classified by the stated maturity date of the security
Total available-for-sale debt securities, amortized cost	709	1,643
Total available-for-sale debt securities, fair value	$ 711	$ 1,645