Future Minimum Lease Payments for Capital and Operating Leases (Parenthetical) (Detail) (United Airlines, Inc., USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014
Mainline
Capital Leases And Operating Leases [Line Items]
Number of assets subject to lease	37
Regional Carrier
Capital Leases And Operating Leases [Line Items]
Number of assets subject to lease	38
Nonoperating Aircraft
Capital Leases And Operating Leases [Line Items]
Operating lease future payments	72
Number of assets subject to lease	21
Minimum
Capital Leases And Operating Leases [Line Items]
Imputed interest rate	3.50%
Maximum
Capital Leases And Operating Leases [Line Items]
Imputed interest rate	18.30%