Consolidated Statements of Shareholders' Equity (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Stockholders' Equity [Abstract]
Common treasury shares (in shares)	46,292,348,000,000	38,308,825	26,866,893	11,445,445
Tax on foreign currency translation	$ (10)	$ 39	$ (2)
Tax on amortization of prior service cost and unrecognized gains and losses included in total benefit cost	34	40	33
Tax on increase in net actuarial losses	1	(37)	(53)
Tax on immediate recognition of prior service cost and unrecognized gains and losses due to curtailments, settlements, and divestitures	5	14	0
Tax on prior service cost from plan amendments	(3)	(2)	0
Tax on deferred derivative gains (losses)	3	(8)	4
Tax on unrealized investment gains reclassification adjustment recognized in income	$ 0	$ 1	$ (1)