Other comprehensive income (Tables)

12 Months Ended

Dec. 31, 2021

Disclosure of analysis of other comprehensive income by item [abstract]

Schedule of other comprehensive income

	Items that may subsequently be reclassified to income				Item never reclassified to income
(millions)	Change in unrealized fair value of derivatives		Cumulative foreign currency translation adjustment		Employee defined benefit plan re- measurements		Accumulated other comprehensive income
Accumulated balance as at January 1, 2019	$	(1)	$	22	$	—	$	21
Other comprehensive income (loss)
Amount arising	—		(3)		(3)		(6)
Net	—		(3)		(3)		(6)
Accumulated balance as at December 31, 2019	$	(1)	$	19	$	(3)	$	15
Other comprehensive income (loss)
Amount arising	(51)		124		—		73
Income taxes	1		—		—		1
Net	(50)		124		—		74
Accumulated balance as at December 31, 2020	$	(51)	$	143	$	(3)	$	89
Other comprehensive income (loss)
Amount arising	41		(95)		—		(54)
Income taxes	(1)		—		—		(1)
Net	$	40	$	(95)	$	—	$	(55)
Accumulated balance as at December 31, 2021	$	(11)	$	48	$	(3)	$	34