Amortized Accumulated Other Comprehensive Income Into Net Periodic Benefit Cost (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Actuarial loss to be reclassified from accumulated other comprehensive income into net periodic benefit cost	$ 73
Pension Benefits | United Air Lines Inc
Defined Benefit Plan Disclosure [Line Items]
Actuarial loss to be reclassified from accumulated other comprehensive income into net periodic benefit cost	2
Pension Benefits | Continental Airlines Inc
Defined Benefit Plan Disclosure [Line Items]
Actuarial loss to be reclassified from accumulated other comprehensive income into net periodic benefit cost	71
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Actuarial loss to be reclassified from accumulated other comprehensive income into net periodic benefit cost	7
Other Postretirement Benefits | United Air Lines Inc
Defined Benefit Plan Disclosure [Line Items]
Actuarial loss to be reclassified from accumulated other comprehensive income into net periodic benefit cost	$ 7