Consolidated Statement of Comprehensive Income (Loss) (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Deferred taxes on postretirement	$ (5)	$ 24	$ 25
Deferred taxes on unrealized gain (loss), other, tax effect	4	0	(13)
Net income (loss)	465	539	977
Fuel derivative contracts
Deferred taxes on unrealized gain (loss) on derivatives, tax effect	(103)	(44)	142
Interest rate derivatives
Deferred taxes on unrealized gain (loss) on derivatives, tax effect	$ 4	$ 6	$ 2