Retirement Benefits - Changes in Fair Value Measurements of Level 3 Investments (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Private Equity Partnerships [Member]
Defined Benefit Plan Disclosure [Line Items]
Beginning balance at December 31	$ 818	$ 848
Relating to assets still held at the reporting date	(105)	(38)
Relating to assets sold during the period	115	158
Purchases	145	148
Sales	(251)	(298)
Ending balance at December 31	722	818
Private Equity Partnerships [Member] | American Airlines, Inc. [Member]
Defined Benefit Plan Disclosure [Line Items]
Beginning balance at December 31	818	848
Relating to assets still held at the reporting date	(105)	(38)
Relating to assets sold during the period	115	158
Purchases	145	148
Sales	(251)	(298)
Ending balance at December 31	722	818
Insurance Group Annuity Contracts [Member]
Defined Benefit Plan Disclosure [Line Items]
Beginning balance at December 31	2	2
Relating to assets still held at the reporting date	0	0
Relating to assets sold during the period	0	0
Purchases	0	0
Sales	0	0
Ending balance at December 31	2	2
Insurance Group Annuity Contracts [Member] | American Airlines, Inc. [Member]
Defined Benefit Plan Disclosure [Line Items]
Beginning balance at December 31	2	2
Relating to assets still held at the reporting date	0	0
Relating to assets sold during the period	0	0
Purchases	0	0
Sales	0	0
Ending balance at December 31	$ 2	$ 2