Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Actuarial changes, tax	$ 14	$ 17	$ 69
Prior service costs, tax	12	(16)	(18)
Other, tax	$ 1	$ 0	$ 0