Debt (Details) $ in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2024 USD ($)	Mar. 31, 2024 CAD ($)	Mar. 31, 2024 CAD ($)	Dec. 31, 2023 USD ($)
Debt Instrument [Line Items]
Commercial paper borrowings				$ 800
5.41% Senior Secured Notes | Senior Notes
Debt Instrument [Line Items]
Repayment of note	$ 48	$ 66
Interest rate	5.41%		5.41%
Commercial Paper | Unsecured Debt
Debt Instrument [Line Items]
Maximum borrowing capacity (up to)	$ 1,500
Commercial paper borrowings	$ 650		$ 881
Weighted average interest rate	5.55%		5.55%	5.59%
Second Amended and Restated Credit Agreement | Revolving Credit Facility
Debt Instrument [Line Items]
Maximum borrowing capacity (up to)	$ 2,200