Debt - Covenants (Details)	Jan. 31, 2019
2014 3.80% Senior Notes, due October 2024
Debt Instrument [Line Items]
Interest rate, stated percentage	3.80%
2014 4.90% Senior Notes, due October 2044
Debt Instrument [Line Items]
Interest rate, stated percentage	4.90%
2012 4.40% Series B Notes, due July 2042
Debt Instrument [Line Items]
Interest rate, stated percentage	4.40%

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

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant