Pension and Other Post-Retirement Benefit Plans - Schedule of Assumptions (Details)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Crewmembers | Pension Plans
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract]
Discount rate	5.25%	5.50%	2.90%
Return of excess premiums	6.40%	6.75%	5.65%
Non-crewmembers | Pension Plans
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract]
Discount rate	5.15%	5.50%	3.00%
Return of excess premiums	6.40%	6.65%	5.65%
Pilots | Post-retirement Healthcare Plans
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract]
Discount rate	5.10%	5.35%	2.00%