Preferred Stock of Subsidiaries (Details) shares in Millions, CAD in Millions, $ in Millions	9 Months Ended
	Sep. 30, 2016 CAD shares	Sep. 30, 2016 USD ($) shares	Sep. 30, 2015 USD ($)
Class of Stock [Line Items]
Proceeds from the issuance of Westcoast Energy Inc. preferred stock | $		$ 229	$ 0
Westcoast Energy Inc.
Class of Stock [Line Items]
Cumulative 5-year minimum rate reset redeemable first preferred shares series 12 | shares	12	12
Proceeds from the issuance of Westcoast Energy Inc. preferred stock	CAD 300	$ 229