Short Term Debt Instruments (Details)	3 Months Ended	9 Months Ended
	Jul. 31, 2016 USD ($)	Jul. 31, 2016 USD ($)	Oct. 31, 2015 USD ($)
Line Of Credit Facility [Line Items]
Credit Facility Current Borrowing Capacity	$ 850,000,000	$ 850,000,000
Commercial Paper	240,000,000	240,000,000	$ 340,000,000
Revolving Credit Facility
Line Of Credit Facility [Line Items]
Credit Facility Current Borrowing Capacity	850,000,000	$ 850,000,000
Line of Credit Facility, Expiration Date		Dec. 14, 2020
Line Of Credit Facility, Optional Additional Expansion Amount	$ 200,000,000	$ 200,000,000
Line Of Credit Facility Frequency Of Commitment Fee Payment		annual
Line of Credit Facility, Commitment Fee Description		$35,000 plus 8.5 basis points
Credit Facility Interest Rate Description		thirty-day London Interbank Offered Rate (LIBOR) plus from 75 to 112.5 basis points
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage		0.085%
Line of Credit Facility, Commitment Fee Amount		$ 35,000
Minimum amount outstanding during period		0
Maximum amount outstanding during period		$ 0
Credit Facility Covenant Terms		total debt to total capitalization of no greater than 70%
Credit Facility Covenant Compliance		actual ratio was 58%
Debt Covenant Total Debt To Total Capital Ratio		70.00%
Ratio of Indebtedness to Net Capital	0.58	0.58
Revolving Credit Facility | Minimum | London Interbank Offered Rate (LIBOR)
Line Of Credit Facility [Line Items]
Debt Instrument, Basis Spread on Variable Rate		0.75%
Revolving Credit Facility | Maximum | London Interbank Offered Rate (LIBOR)
Line Of Credit Facility [Line Items]
Debt Instrument, Basis Spread on Variable Rate		1.125%
Letter Of Credit
Line Of Credit Facility [Line Items]
Credit Facility Current Borrowing Capacity	$ 10,000,000	$ 10,000,000	10,000,000
Letters of Credit Outstanding, Amount	1,700,000	1,700,000	$ 1,600,000
Commercial Paper
Line Of Credit Facility [Line Items]
Credit Facility Current Borrowing Capacity	$ 850,000,000	$ 850,000,000
Credit Facility Interest Rate Description		interest based on, among other things, the size and maturity date of the note, the frequency of the issuance and our credit ratings, plus a spread of 5 basis points
Short Term Borrowings Term		$850 million unsecured CP program that is backstopped by the revolving syndicated credit facility. The amounts outstanding under the revolving syndicated credit facility and the CP program, either individually or in the aggregate, cannot exceed $850 million.
Maximum Number Of Possible Days Outstanding For Commercial Paper Program		397 days
Weighted Average Interest Rate	0.62%	0.62%	0.22%
Minimum amount outstanding during period	$ 240,000,000	$ 240,000,000
Maximum amount outstanding during period	$ 530,000,000	$ 530,000,000
Commercial Paper | Base Rate
Line Of Credit Facility [Line Items]
Debt Instrument, Basis Spread on Variable Rate		0.05%
Commercial Paper | Minimum
Line Of Credit Facility [Line Items]
Debt Instrument, Term	7 days
Line of Credit Facility Interest Rate During Period	0.52%	0.20%
Commercial Paper | Maximum
Line Of Credit Facility [Line Items]
Debt Instrument, Term	14 days
Line of Credit Facility Interest Rate During Period	0.68%	0.75%
Commercial Paper | Weighted Average
Line Of Credit Facility [Line Items]
Line of Credit Facility Interest Rate During Period	0.60%	0.54%