Special Charges - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2018 USD ($)	Mar. 31, 2017 USD ($) Technician
Special Charges [Line Items]
Severance and benefits costs	$ 14,000,000	$ 37,000,000
Fair value adjustment for aircraft purchased	23,000,000
Fair value adjustment for aircraft purchased, net of taxes	$ 17,000,000
Severance-related accrual expected payment date	2019
Grounded aircraft related accrual expected payment date	2025
International Brotherhood of Teamsters
Special Charges [Line Items]
Severance and benefits costs	$ 8,000,000	21,000,000
Severance and benefits costs net of tax	7,000,000	$ 14,000,000
Voluntary early out program | International Brotherhood of Teamsters
Special Charges [Line Items]
Number of positions eliminated | Technician		1,000
Voluntary early out program | International Brotherhood of Teamsters | Maximum
Special Charges [Line Items]
Severance payment per participant		$ 100,000
Management Reorganization Initiative
Special Charges [Line Items]
Severance and benefits costs	6,000,000	16,000,000
Severance and benefits costs net of tax	$ 4,000,000	$ 10,000,000