Debt and Credit Facilities Available Credit Facilities and Restrictive Debt Covenants - Additional Information (Details) CAD in Millions			9 Months Ended
		May 31, 2016 CAD	Sep. 30, 2016 CAD	Sep. 30, 2016 USD ($)		May 31, 2016 USD ($)
Line of Credit Facility [Line Items]
Total Credit Facilities Capacity				$ 6,338,000,000
Line of Credit Facility, Covenant Compliance			Our credit agreements contain various covenants, including the maintenance of certain financial ratios. Failure to meet those covenants beyond applicable grace periods could result in accelerated due dates and/or termination of the agreements. As of September 30, 2016, we were in compliance with those covenants.
Union Gas Limited
Line of Credit Facility [Line Items]
Total Credit Facilities Capacity			CAD 700	533,000,000	[1]
Line Of Credit Facility Maturity Year	[1]		2021
Union Gas Limited | Union Gas Two Point Eight One Percent Senior Unsecured Notes Due 2026 [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Face Amount		CAD 250				$ 191,000,000
Debt Instrument, Interest Rate, Stated Percentage		2.81%				2.81%
Debt Instrument, Maturity Year		2026
Union Gas Limited | Union Gas Three Point Eight Zero Percent Senior Unsecured Notes Due 2026 [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Face Amount		CAD 250				$ 191,000,000
Debt Instrument, Interest Rate, Stated Percentage		3.80%				3.80%
Debt Instrument, Maturity Year		2046
Spectra Energy Partners, LP
Line of Credit Facility [Line Items]
Total Credit Facilities Capacity	[2]			2,500,000,000
Line Of Credit Facility Maturity Year	[2]		2021
Westcoast Energy Inc.
Line of Credit Facility [Line Items]
Total Credit Facilities Capacity			CAD 400	305,000,000	[3]
Line Of Credit Facility Maturity Year	[3]		2021
364-day syndicated | Spectra Energy Capital, LLC
Line of Credit Facility [Line Items]
Total Credit Facilities Capacity	[4]			2,000,000,000
Line Of Credit Facility Maturity Year	[4]		2017
Multi Year Syndicated | Spectra Energy Capital, LLC
Line of Credit Facility [Line Items]
Total Credit Facilities Capacity	[4]			1,000,000,000
Line Of Credit Facility Maturity Year	[4]		2021
Letter of Credit
Line of Credit Facility [Line Items]
Line of Credit Facility, Fair Value of Amount Outstanding				0
Revolving Credit Facility
Line of Credit Facility [Line Items]
Line of Credit Facility, Fair Value of Amount Outstanding				$ 0

[1] U.S. dollar equivalent at September 30, 2016. The revolving credit facility is 700 million Canadian dollars and contains a covenant that requires the Union Gas debt-to-total capitalization ratio to not exceed 75% and a provision which requires Union Gas to repay all borrowings under the facility for a period of two days during the second quarter of each year. The ratio was 68.1% at September 30, 2016.

[2] Revolving credit facility contains a covenant that requires SEP to maintain a ratio of total Consolidated Indebtedness-to-Consolidated EBITDA, as defined in the agreement, of 5.0 to 1 or less. As of September 30, 2016, this ratio was 3.7 to 1.

[3] U.S. dollar equivalent at September 30, 2016. The revolving credit facility is 400 million Canadian dollars and contains a covenant that requires the Westcoast non-consolidated debt-to-total capitalization ratio to not exceed 75%. The ratio was 31.1% at September 30, 2016.

[4] Revolving credit facilities contain a covenant requiring the Spectra Energy consolidated debt-to-total capitalization ratio, as defined in the agreements, to not exceed 65%. Per the terms of the agreements, collateralized debt is excluded from the calculation of the ratio. This ratio was 55.8% at September 30, 2016.