Special Charges - Additional Information (Detail) technician in Thousands	1 Months Ended	3 Months Ended			6 Months Ended
	May 31, 2018 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($) technician	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)
Special Charges [Line Items]
Impairment of assets		$ 111,000,000	$ 0		$ 134,000,000	$ 0
Severance and benefits costs		11,000,000	41,000,000		25,000,000	78,000,000
Other special charges		(7,000,000)	(3,000,000)		(10,000,000)	(17,000,000)
Other special charges, net of tax		5,000,000			8,000,000
International Brotherhood of Teamsters
Special Charges [Line Items]
Severance and benefits costs		6,000,000			14,000,000
Severance and benefits costs net of tax		4,000,000			11,000,000
Voluntary early out program
Special Charges [Line Items]
Severance and benefits costs			36,000,000			57,000,000
Severance and benefits costs net of tax			23,000,000			37,000,000
Voluntary early out program | International Brotherhood of Teamsters
Special Charges [Line Items]
Number of positions eliminated | technician				1
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		5,000,000	5,000,000		11,000,000	21,000,000
Severance and benefits costs net of tax		4,000,000	$ 3,000,000		8,000,000	$ 13,000,000
Certain Fleet Types and Certain International Slots
Special Charges [Line Items]
Impairment of assets		6,000,000			29,000,000
Impairment of assets, net of tax		$ 5,000,000			$ 22,000,000
Brazil Routes
Special Charges [Line Items]
Intangible asset impairment	$ 105,000,000
Intangible asset impairment, net of tax	$ 82,000,000