Leases and Capacity Purchase Agreements - Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2022 USD ($) aircraft	Dec. 31, 2021 USD ($) aircraft	Dec. 31, 2020 USD ($)
Lessee, Lease, Description [Line Items]
Additional leases that have not yet commenced | $	$ 3,000.0
Lease terms of additional leases that have not yet commenced (up to)	12 years
Boeing 737 Max
Lessee, Lease, Description [Line Items]
Number of aircraft acquired with exercised purchase options		6
Capacity Purchase Agreements | CRJ-900
Lessee, Lease, Description [Line Items]
Initial term of operating leases	5 years
Number of aircraft subject to embedded leases	38
Cash Collateralized Letters of Credit | United Airlines, Inc.
Lessee, Lease, Description [Line Items]
Number of regional aircraft	470
Mainline Aircraft
Lessee, Lease, Description [Line Items]
Number of aircraft subject to operating leases	99
Number of aircraft subject to finance leases	26
Mainline Aircraft | Minimum
Lessee, Lease, Description [Line Items]
Initial term of operating leases	1 month
Mainline Aircraft | Maximum
Lessee, Lease, Description [Line Items]
Initial term of operating leases	12 years
Regional Aircraft
Lessee, Lease, Description [Line Items]
Number of aircraft subject to operating leases	318
Number of aircraft subject to finance leases	16
Regional Aircraft | United Airlines, Inc. | Capacity Purchase Agreements
Lessee, Lease, Description [Line Items]
Expenses | $	$ 900.0	$ 600.0	$ 600.0
Notes receivables | $	$ 62.0	28.0
Accounts payable | $		$ 102.0
Non-Aircraft | Minimum
Lessee, Lease, Description [Line Items]
Initial term of operating leases	1 month
Non-Aircraft | Maximum
Lessee, Lease, Description [Line Items]
Initial term of operating leases	30 years