Debt (Schedule of Notes Payable and Long-Term Debt) (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended
Oct. 31, 2014	Jan. 31, 2014
Debt Instrument [Line Items]
Total notes payable and long-term debt	$ 1,229	$ 1,333
Less current portion	2	2
Total notes payable and long-term debt, net of current portion	1,227	1,331
Fair value of notes payable and long-term debt	1,228	1,350
Notes Which Mature In December 2020
Debt Instrument [Line Items]
Senior unsecured notes	451	449
Stated interest rate	4.45%
Effective interest rate	4.53%
Notes Which Mature In December 2040
Debt Instrument [Line Items]
Senior unsecured notes	291	300
Stated interest rate	5.95%
Effective interest rate	6.03%
Notes Which Mature In July 2032
Debt Instrument [Line Items]
Senior unsecured notes	248	248
Stated interest rate	7.13%
Effective interest rate	7.43%
Notes Which Mature In July 2033
Debt Instrument [Line Items]
Senior unsecured notes	201	296
Stated interest rate	5.50%
Effective interest rate	5.83%
Capital leases and other notes payable due on various dates through fiscal 2021
Debt Instrument [Line Items]
Other notes payable due on various dates through fiscal 2021	$ 38	$ 40
Minimum stated interest rate	0.00%
Maximum stated interest rate	3.70%

Amount of short-term debt and current maturity of long-term debt and capital lease obligations due within one year or the normal operating cycle, if longer.

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Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable.

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Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

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Contractual interest rate for funds borrowed, under the debt agreement.

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Maximum contractual interest rate for funds borrowed, under the debt agreement.

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Minimum contractual interest rate for funds borrowed, under the debt agreement.

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Carrying amount of long-term debt, net of unamortized discount or premium, including current and noncurrent amounts. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Carrying amount of long-term debt, net of unamortized discount or premium, excluding amounts to be repaid within one year or the normal operating cycle, if longer (current maturities). Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Including the current and noncurrent portions, the carrying value of notes payable which were initially due after one year or beyond the normal operating cycle, if longer, and which are not otherwise defined in the taxonomy.

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Including the current and noncurrent portions, carrying value as of the balance sheet date of Notes with the highest claim on the assets of the issuer in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle if longer). Senior note holders are paid off in full before any payments are made to junior note holders.

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