Condensed Consolidated Statements of Changes in Common Shareholders' Equity - USD ($) $ in Millions	Common Shares [Member]	Paid-in-Surplus [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Income/(Loss) (Note 9) [Member]	[1]	Total
Shareholders' equity, beginning balance at Dec. 31, 2019	$ 2,780	$ 4,523	$ 48,605	$ (36,424)	$ (1,356)		$ 18,128
Common shares, beginning balance at Dec. 31, 2019	1,112,000,000.0			(419,900,000)
Net income			3,969				3,969
Other comprehensive income/(loss)					5		5	[2]
Conversion, stock option exercises, forfeitures, and other	$ 1	16		$ 10			27
Conversion, stock option exercises, forfeitures, and other (shares)	200,000			1,000,000.0
Share repurchases (Note 16)		310		$ (3,266)			$ (2,956)
Share repurchases (Note 16) (shares)				(18,300,000)			(18,351,368)
Cash dividends declared			(1,974)				$ (1,974)
Shareholders' equity, ending balance at Sep. 30, 2020	$ 2,781	4,849	50,600	$ (39,680)	(1,351)		17,199
Common shares, ending balance at Sep. 30, 2020	1,112,200,000			(437,200,000)
Shareholders' equity, beginning balance at Jun. 30, 2020	$ 2,781	4,135	49,892	$ (38,984)	(1,372)		16,452
Common shares, beginning balance at Jun. 30, 2020	1,112,300,000			(433,600,000)
Net income			1,363				1,363
Other comprehensive income/(loss)					21		21	[3]
Conversion, stock option exercises, forfeitures, and other		4		$ 14			$ 18
Conversion, stock option exercises, forfeitures, and other (shares)	(100,000)			400,000
Share repurchases (Note 16)		710		$ (710)
Share repurchases (Note 16) (shares)				(4,000,000.0)			(4,045,575)	[4]
Cash dividends declared			(655)				$ (655)
Shareholders' equity, ending balance at Sep. 30, 2020	$ 2,781	4,849	50,600	$ (39,680)	(1,351)		17,199
Common shares, ending balance at Sep. 30, 2020	1,112,200,000			(437,200,000)
Shareholders' equity, beginning balance at Dec. 31, 2020	$ 2,781	4,864	51,326	$ (40,420)	(1,593)		$ 16,958
Common shares, beginning balance at Dec. 31, 2020	1,112,200,000			(440,900,000)			671,351,360
Net income			4,812				$ 4,812
Other comprehensive income/(loss)					60		60	[2]
Conversion, stock option exercises, forfeitures, and other		57					57
Conversion, stock option exercises, forfeitures, and other (shares)	200,000			400,000
Share repurchases (Note 16)		26		$ (5,952)			$ (5,926)
Share repurchases (Note 16) (shares)				(27,500,000)			(27,500,069)
Cash dividends declared			(2,044)				$ (2,044)
Shareholders' equity, ending balance at Sep. 30, 2021	$ 2,781	4,947	54,094	$ (46,372)	(1,533)		$ 13,917
Common shares, ending balance at Sep. 30, 2021	1,112,400,000			(468,000,000.0)			644,407,285
Shareholders' equity, beginning balance at Jun. 30, 2021	$ 2,781	4,499	53,116	$ (44,542)	(1,551)		$ 14,303
Common shares, beginning balance at Jun. 30, 2021	1,112,500,000			(459,500,000)
Net income			1,673				1,673
Other comprehensive income/(loss)					18		18	[3]
Conversion, stock option exercises, forfeitures, and other		22		$ 5			27
Conversion, stock option exercises, forfeitures, and other (shares)	(100,000)			100,000
Share repurchases (Note 16)		426		$ (1,835)			$ (1,409)
Share repurchases (Note 16) (shares)				(8,600,000)			(8,604,239)	[4]
Cash dividends declared			(695)				$ (695)
Shareholders' equity, ending balance at Sep. 30, 2021	$ 2,781	$ 4,947	$ 54,094	$ (46,372)	$ (1,533)		$ 13,917
Common shares, ending balance at Sep. 30, 2021	1,112,400,000			(468,000,000.0)			644,407,285

[1] AOCI = Accumulated Other Comprehensive Income/Loss (Note 9)

[2] Net of deferred taxes of ($26) million and ($18) million during the nine months ended September 30, 2021 and 2020, respectively.

[3] Net of deferred taxes of ($8) million and ($6) million during the three months ended September 30, 2021 and 2020, respectively.

[4] Includes an incremental 1,983,859 and 4,045,575 shares received upon final settlement in September 2021 and July 2020, respectively, under accelerated share repurchase programs.