Consolidated Statements of Shareholders' Equity (Parenthetical) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
Statement of Stockholders' Equity [Abstract]
Treasury shares (shares)	45,942,257,000,000	45,992,714	41,447,682	38,634,545	45,942,257,000,000	41,447,682	46,292,384	38,308,825
Foreign currency translation, tax	$ 2	$ 2	$ (6)	$ (2)	$ 4	$ (8)
Amortization of prior service cost and unrecognized gains and (losses) included in total benefit cost, tax	8	8	8	8	16	16
(Increase)/Decrease in net actuarial losses, tax	3	1	5	1	4	6
Prior service (cost) credit from plan amendments, tax	0		0		0	0
Immediate recognition of prior service cost and unrecognized gains and losses due to curtailments, settlements, and divestitures, tax	0		2		0	2
Deferred derivative gains (losses), tax	0	0	4	(2)	$ 0	$ 2
Reclassification adjustment for amounts recognized in income, tax	$ (1)	$ 0	$ 1	$ 1
Cash dividends declared (dollars per share)	$ 0.16		$ 0.14		$ 0.32	$ 0.28

Aggregate dividends declared during the period for each share of common stock outstanding.

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