Income Taxes - Components (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Current income tax expense:
State income tax	$ 2	$ 1	$ 2
Canadian federal and provincial income tax	143	83	48
Total current income tax expense	145	84	50
Deferred income tax expense/(benefit):
Federal income tax	55	46	16
State income tax	13	11	23
Canadian federal and provincial income tax	(24)	105	23
Total deferred income tax expense	44	162	62
Total income tax expense	$ 189	$ 246	$ 112