Consolidated Statements Of Shareholders' Equity - USD ($) $ in Millions	Total	Common Stock [Member]	Common shares in treasury [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Net Investment Gain (Loss) Attributable to Parent [Member]	Cumulative Foreign Currency Translation Adjustment [Member]	Postretirement Benefit Liability Adjustment [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Balance - beginning of period at Dec. 31, 2016		$ 11,121	$ (1,480)	$ 15,335	$ 23,613	$ 1,058	$ (1,663)	$ 291
Common Shares repurchased			(475)
Net shares redeemed under employee share-based compensation plans			280	(275)
Exercise of stock options				(38)
Share-based compensation expense				156
Net income	$ 2,398				2,398
Funding of dividends declared to Retained earnings				(656)
Funding of dividends declared from Additional paid-in capital					656
Dividends declared on Common Shares					(656)
Change in period, before reclassification from AOCI, net of income tax benefit (expense) of $300 and $(259)						507
Amounts reclassified from AOCI, net of income tax benefit (expense) of $(15) and $3						(14)
Change in period, net of income tax benefit (expense) of $285 and $(256)						493
Change in period, net of income tax expense of $(15) and $(7)							229
Change in period, net of income tax benefit of $9 and $17								(38)
Balance - end of period at Jun. 30, 2017	50,349		(1,675)	14,522	26,011	1,551	(1,434)	253	$ 370
Cumulative effect of adoption of accounting guidance (refer to Note 1)					410	(417)
Balance - beginning of period (Scenario, Previously Reported [Member]) at Dec. 31, 2017					27,474	1,450
Balance - beginning of period at Dec. 31, 2017	51,172	$ 11,121	(1,944)	13,978	27,884	1,033	(1,187)	280
Common Shares repurchased			(324)
Net shares redeemed under employee share-based compensation plans			228	(261)
Exercise of stock options				(19)
Share-based compensation expense				123
Net income	2,376				2,376
Funding of dividends declared to Retained earnings				(671)
Funding of dividends declared from Additional paid-in capital					671
Dividends declared on Common Shares					(671)
Change in period, before reclassification from AOCI, net of income tax benefit (expense) of $300 and $(259)						(1,512)
Amounts reclassified from AOCI, net of income tax benefit (expense) of $(15) and $3						89
Change in period, net of income tax benefit (expense) of $285 and $(256)						(1,423)
Change in period, net of income tax expense of $(15) and $(7)							(192)
Change in period, net of income tax benefit of $9 and $17								(31)
Balance - end of period at Jun. 30, 2018	$ 50,971		$ (2,040)	$ 13,150	$ 30,260	$ (390)	$ (1,379)	$ 249	$ (1,520)