Equity Method Investments (Details) - USD ($)		3 Months Ended		9 Months Ended
	Aug. 12, 2016	Jul. 31, 2016	Jul. 31, 2015	Jul. 31, 2016	Jul. 31, 2015	Feb. 12, 2016	Oct. 31, 2015
Schedule of Equity Method Investments [Line Items]
Related party costs		$ 7,055,000	$ 7,362,000	$ 21,658,000	$ 22,132,000
Trade accounts payable		2,369,000		2,369,000			$ 2,473,000
Equity method investments in non-utility activities		$ 239,650,000		239,650,000			206,956,000
Contributions to equity method investments				$ 30,642,000	20,063,000
Cardinal Pipeline Company
Schedule of Equity Method Investments [Line Items]
Membership interest percentage		21.49%		21.49%
Related party costs		$ 2,198,000	2,207,000	$ 6,550,000	6,556,000
Trade accounts payable		$ 741,000		$ 741,000			744,000
Pine Needle Company
Schedule of Equity Method Investments [Line Items]
Membership interest percentage		45.00%		45.00%
Related party costs		$ 2,535,000	2,833,000	$ 8,141,000	8,609,000
Trade accounts payable		$ 854,000		$ 854,000			955,000
South Star Energy Services
Schedule of Equity Method Investments [Line Items]
Membership interest percentage		15.00%		15.00%
Operating revenues		$ 34,000	475,000	$ 286,000	1,058,000
Trade accounts receivable		$ 2,000		$ 2,000			183,000
Equity Method Investment Agreement To Sell Interest						$ 160,000,000
Hardy Storage
Schedule of Equity Method Investments [Line Items]
Membership interest percentage		50.00%		50.00%
Related party costs		$ 2,322,000	$ 2,322,000	$ 6,967,000	$ 6,967,000
Trade accounts payable		$ 774,000		$ 774,000			$ 774,000
Constitution Pipeline Company
Schedule of Equity Method Investments [Line Items]
Membership interest percentage		24.00%		24.00%
Estimated Pipeline Costs Including AFUDC		$ 1,100,000,000		$ 1,100,000,000
Target Pipeline In Service Date				2018
Equity method investments in non-utility activities		93,600,000		$ 93,600,000
Other than Temporary Impairment Losses, Investments				0
Estimated Pipeline Costs Excluding AFUDC		955,000,000		955,000,000
Estimated Contributions For Pipeline And Construction Costs		229,300,000		229,300,000
Contributions to equity method investments		500,000		10,200,000
Total equity contribution for the project		$ 82,900,000		$ 82,900,000
Atlantic Coast Pipeline
Schedule of Equity Method Investments [Line Items]
Membership interest percentage		10.00%		10.00%
Target Pipeline In Service Date				2019
Contributions to equity method investments		$ 10,000,000		$ 20,400,000
Total equity contribution for the project		31,000,000		$ 31,000,000
Long term purchase commitment time period				20 years
Estimated Percentage Project Financing				60.00%
Estimated Percentage Debt Financing				50.00%
Estimated Percentage Equity Financing				50.00%
Funding Obligation Under Equity Contribution Agreements				$ 15,200,000
Minimum | Atlantic Coast Pipeline
Schedule of Equity Method Investments [Line Items]
Estimated Pipeline Development And Construction Costs		4,500,000,000		4,500,000,000
Maximum | Atlantic Coast Pipeline
Schedule of Equity Method Investments [Line Items]
Estimated Pipeline Development And Construction Costs		$ 5,000,000,000		$ 5,000,000,000
Subsequent Event | Atlantic Coast Pipeline
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Additional Information	On August 12, 2016, the FERC issued its notice of schedule for environmental review of the project. Under the notice of schedule, we anticipate that the FERC will issue a draft of its environmental impact statement (EIS) in December 2016 and the final EIS in the summer of 2017. Based on this schedule, ACP is reviewing the timing of the project, as well as refining the project cost estimates.