Consolidated Statements Of Shareholders' Equity - USD ($) $ in Millions	Total	Common Shares	Common Shares in Treasury	Additional Paid-in Capital	Retained Earnings	Retained Earnings Cumulative Effect, Period of Adoption, Adjustment [Member]	Retained Earnings Cumulative Effect, Period of Adoption, Adjusted Balance [Member]	AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-sale, Parent [Member]	AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-sale, Parent [Member] Cumulative Effect, Period of Adoption, Adjustment [Member]	AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-sale, Parent [Member] Cumulative Effect, Period of Adoption, Adjusted Balance [Member]	Cumulative Translation Adjustment	Cumulative Translation Adjustment Cumulative Effect, Period of Adoption, Adjustment [Member]	Cumulative Translation Adjustment Cumulative Effect, Period of Adoption, Adjusted Balance [Member]	Accumulated Defined Benefit Plans Adjustment [Member]	Accumulated Defined Benefit Plans Adjustment [Member] Cumulative Effect, Period of Adoption, Adjustment [Member]	Accumulated Defined Benefit Plans Adjustment [Member] Cumulative Effect, Period of Adoption, Adjusted Balance [Member]	Accumulated Other Comprehensive Income
Balance – beginning of year at Dec. 31, 2017		$ 11,121	$ (1,944)	$ 13,978	$ 27,474	$ 264	$ 27,738	$ 1,450	$ (296)	$ 1,154	$ (1,187)	$ (22)	$ (1,209)	$ 280	$ 47	$ 327
Treasury Stock, Retired, Cost Method, Amount		0	0		0
Common Shares repurchased	$ (1,021)		(1,021)
Net shares redeemed under employee share-based compensation plans			347	(313)
Stock Issued During Period, Value, Stock Options Exercised				(49)
Share-based compensation expense				285
FundingDividendsDeclaredToRetainedEarnings				(1,344)
Net income	3,962				3,962
Funding Dividends Declared From Additional Paid In Capital					1,344
Dividends declared on Common Shares					(1,344)
Change in year, before reclassification from AOCI, net of income tax (expense) benefit of $(426), $(647), and $338								(1,960)
Amounts reclassified from AOCI, net of income tax (expense) of $(36), nil, and $(41)								261
Change in year, net of income tax (expense) benefit of $(462), $(647), and $297								(1,699)
Change in year, net of income tax (expense) benefit of $(4), $24, and $35											(767)
Change in year, net of income tax benefit of $50, $18, and $67														(254)
Balance – Ending of year at Dec. 31, 2018	50,312	11,121	(2,618)	12,557	31,700	(12)	31,688	(545)	0	(545)	(1,976)		(1,976)	73	0	73	$ (2,448)
Treasury Stock, Retired, Cost Method, Amount		0	0		0
Common Shares repurchased	(1,531)		(1,531)
Net shares redeemed under employee share-based compensation plans			395	(178)
Stock Issued During Period, Value, Stock Options Exercised				(82)
Share-based compensation expense				266
FundingDividendsDeclaredToRetainedEarnings				(1,360)
Net income	4,454				4,454
Funding Dividends Declared From Additional Paid In Capital					1,360
Dividends declared on Common Shares					(1,360)
Change in year, before reclassification from AOCI, net of income tax (expense) benefit of $(426), $(647), and $338								3,057
Amounts reclassified from AOCI, net of income tax (expense) of $(36), nil, and $(41)								31
Change in year, net of income tax (expense) benefit of $(462), $(647), and $297								3,088
Change in year, net of income tax (expense) benefit of $(4), $24, and $35											37
Change in year, net of income tax benefit of $50, $18, and $67														(58)
Balance – Ending of year at Dec. 31, 2019	55,331	11,121	(3,754)	11,203	36,142	$ (72)	$ 36,070	2,543	$ 0	$ 2,543	(1,939)		$ (1,939)	15	$ 0	$ 15	619
Treasury Stock, Retired, Cost Method, Amount		(57)	323		(266)
Common Shares repurchased	(516)		(516)
Net shares redeemed under employee share-based compensation plans			303	(195)
Stock Issued During Period, Value, Stock Options Exercised				(50)
Share-based compensation expense				255
FundingDividendsDeclaredToRetainedEarnings				(1,398)
Net income	3,533				3,533
Funding Dividends Declared From Additional Paid In Capital					1,398
Dividends declared on Common Shares					(1,398)
Change in year, before reclassification from AOCI, net of income tax (expense) benefit of $(426), $(647), and $338								1,885
Amounts reclassified from AOCI, net of income tax (expense) of $(36), nil, and $(41)								245
Change in year, net of income tax (expense) benefit of $(462), $(647), and $297								2,130
Change in year, net of income tax (expense) benefit of $(4), $24, and $35											302
Change in year, net of income tax benefit of $50, $18, and $67														(182)
Balance – Ending of year at Dec. 31, 2020	$ 59,441	$ 11,064	$ (3,644)	$ 9,815	$ 39,337			$ 4,673			$ (1,637)			$ (167)			$ 2,869