Consolidated Statements of Shareholders' Equity (Parenthetical) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018
Statement Of Stockholders Equity [Abstract]
Common treasury shares (in shares)	45,465,877	45,992,714	45,813,109	46,292,384
Tax on foreign currency translation	$ (8)	$ 2
Tax on amortization of prior service cost and unrecognized gains and losses included in total benefit cost	9	8
Tax on increase / decrease in net actuarial losses	0	1
Tax on immediate recognition of prior service cost and unrecognized gains and losses due to curtailments, settlements, and divestitures	(1)	0
Tax effect of deferred derivative gains	5	0
Tax effect of reclassification adjustment for amounts recognized in income	$ 0	$ 0
Cash dividends declared per common share (in dollars per share)	$ 0.16	$ 0.16