Allowance for Doubtful Accounts - Narrative (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended
Apr. 30, 2015	Apr. 30, 2014	Jan. 31, 2015 class segments
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Portfolio Segments for Finance Receivables	2		2
Classes Of Receivables In Each Portfolio			1nav_ClassesOfReceivablesInEachPortfolio
Retail Portfolio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Impaired Financing Receivable, Average Recorded Investment	$ 25	$ 16

Average amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 15

-Subparagraph (c)(1)

-URI http://asc.fasb.org/extlink&oid=35738203&loc=d3e5212-111524

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 17

-URI http://asc.fasb.org/extlink&oid=35738203&loc=d3e5258-111524

Name:	us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration