CONSOLIDATED STATEMENT OF COMPREHENSIVE INCOME (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Changes in unamortized actuarial loss, tax expense (benefit)	$ 235	$ (2)	$ (151)
Changes in unamortized net prior service credit, tax expense (benefit)	$ (3)	$ (2)	$ 0