Regulatory Matters - Assets and Liabilities (Details) - USD ($) $ in Thousands	Jul. 31, 2016	Oct. 31, 2015
Regulatory Liabilities [Line Items]
Regulatory liabilities - current	$ 3,908	$ 13,367
Regulatory liabilities - noncurrent	598,749	590,301
Regulatory liabilities, Total	602,657	603,668
Regulatory Assets [Line Items]
Regulatory assets - current	78,420	10,936
Regulatory assets - noncurrent	341,124	196,726
Regulatory assets, Total	419,544	207,662
Amounts due to customers
Regulatory Liabilities [Line Items]
Regulatory liabilities - current	3,908	13,367
Regulatory cost of removal
Regulatory Liabilities [Line Items]
Regulatory liabilities - noncurrent	533,844	521,478
Deferred income taxes
Regulatory Liabilities [Line Items]
Regulatory liabilities - noncurrent	64,827	68,738
Amounts not yet recognized as a component of pension and other retirement benefit costs
Regulatory Liabilities [Line Items]
Regulatory liabilities - noncurrent	78	85
Unamortized debt expense on reacquired debt
Regulatory Assets [Line Items]
Regulatory assets - current	238	238
Regulatory assets - noncurrent	4,488	4,666
Amounts due from customers
Regulatory Assets [Line Items]
Regulatory assets - current	34,621	0
Environmental costs
Regulatory Assets [Line Items]
Regulatory assets - current	1,516	1,513
Regulatory assets - noncurrent	3,989	5,107
Deferred operations and maintenance expenses
Regulatory Assets [Line Items]
Regulatory assets - current	889	847
Regulatory assets - noncurrent	3,325	3,997
Deferred pipeline integrity expenses
Regulatory Assets [Line Items]
Regulatory assets - current	3,470	3,470
Regulatory assets - noncurrent	31,533	29,824
Deferred pension and other retirement benefit costs
Regulatory Assets [Line Items]
Regulatory assets - current	2,757	2,757
Regulatory assets - noncurrent	17,509	17,861
Amounts not yet recognized as a component of pension and other retirement benefit costs
Regulatory Assets [Line Items]
Regulatory assets - noncurrent	109,884	114,854
Regulatory cost of removal
Regulatory Assets [Line Items]
Regulatory assets - noncurrent	19,925	19,087
Robeson liquefied natural gas (LNG) development costs
Regulatory Assets [Line Items]
Regulatory assets - current	223	381
Regulatory assets - noncurrent	0	127
Derivatives - gas supply contracts held for utility operations
Regulatory Assets [Line Items]
Regulatory assets - current	33,300	0
Regulatory assets - noncurrent	149,600	0
Other
Regulatory Assets [Line Items]
Regulatory assets - current	1,406	1,730
Regulatory assets - noncurrent	$ 871	$ 1,203