CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY (UNAUDITED) - USD ($) shares in Millions, $ in Millions		Total	Conversion Of Series A Preferred Stock Upon Sale Into Public Market	Conversion Of Class C Common Stock Upon Sale Into Public Market	Cumulative Effect, Period of Adoption, Adjustment	Series B preferred stock	Series C preferred stock	Class A common stock	Preferred Stock	Preferred Stock Conversion Of Series A Preferred Stock Upon Sale Into Public Market	Preferred Stock Series A preferred stock	[1]	Preferred Stock Series A preferred stock Conversion Of Series A Preferred Stock Upon Sale Into Public Market	[1]	Preferred Stock Series B preferred stock	Preferred Stock Series C preferred stock	Common Stock Class A common stock	Common Stock Class A common stock Conversion Of Series A Preferred Stock Upon Sale Into Public Market	Common Stock Class A common stock Conversion Of Class C Common Stock Upon Sale Into Public Market	[1]	Common Stock Class B common stock	Common Stock Class C common stock	Common Stock Class C common stock Conversion Of Class C Common Stock Upon Sale Into Public Market	[1]	Right to Recover for Covered Losses	Additional Paid-In Capital	Additional Paid-In Capital Conversion Of Series A Preferred Stock Upon Sale Into Public Market	Accumulated Income	Accumulated Income Cumulative Effect, Period of Adoption, Adjustment	Accumulated Other Comprehensive Income (Loss), Net
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adoption of new accounting standards		$ 36,210			$ 3				$ 5,086						$ 1,106	$ 1,543									$ (39)	$ 16,721		$ 14,088	$ 3	$ 354
Beginning balance (in shares) at Sep. 30, 2020											0				2	3	1,683				245	11
Beginning balance at Sep. 30, 2020		36,210			$ 3				5,086						$ 1,106	$ 1,543									(39)	16,721		14,088	$ 3	354
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		3,126																										3,126
Other comprehensive income (loss), net of tax		800																												800
Comprehensive income		3,926
VE territory covered losses incurred		(10)													0	0									(10)
Recovery through conversion rate adjustment		0				$ 9	$ 6		(15)						$ (9)	$ (6)									15
Conversion of stock (in shares)													0					20	0				0
Conversion of stock			$ 0							$ (1,388)																	$ 1,388
Share-based compensation, net of forfeitures		122																								122
Vesting of restricted stock and performance-based shares (in shares)																	3
Restricted stock and performance-based shares settled in cash for taxes (in shares)																	(1)
Restricted stock and performance-based shares settled in cash for taxes		(134)																								(134)
Cash proceeds from issuance of common stock under employee equity plans (in shares)	[1]																0
Cash proceeds from issuance of class A common stock under employee equity plans		61																								61
Cash dividends declared and paid, at a quarterly amount per Class A share		(703)																										(703)
Repurchase of class A common stock (in shares)								(9)									(9)
Repurchase of class A common stock		(1,796)						$ (1,796)																		(95)		(1,701)
Ending balance (in shares) at Dec. 31, 2020											0				2	3	1,696				245	11
Ending balance at Dec. 31, 2020		37,679							3,683						$ 1,097	$ 1,537									(34)	18,063		14,813		1,154
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adoption of new accounting standards		37,679							3,683						1,097	1,537									(34)	18,063		14,813		1,154
Adoption of new accounting standards		37,589							3,080						$ 1,071	$ 1,523									(133)	18,855		15,351		436
Beginning balance (in shares) at Sep. 30, 2021											0				2	3	1,677				245	10
Beginning balance at Sep. 30, 2021		37,589							3,080						$ 1,071	$ 1,523									(133)	18,855		15,351		436
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		3,959																										3,959
Other comprehensive income (loss), net of tax		(508)																												(508)
Comprehensive income		3,451
VE territory covered losses incurred		(7)													0	0									(7)
Recovery through conversion rate adjustment		0				$ 26	$ 3		(29)						$ (26)	$ (3)									29
Conversion of stock (in shares)													0					1	0				0
Conversion of stock			$ 0	$ 0						$ (56)																	$ 56
Share-based compensation, net of forfeitures		128																								128
Vesting of restricted stock and performance-based shares (in shares)																	2
Restricted stock and performance-based shares settled in cash for taxes (in shares)	[1]																0
Restricted stock and performance-based shares settled in cash for taxes		(113)																								(113)
Cash proceeds from issuance of common stock under employee equity plans (in shares)	[1]
Cash proceeds from issuance of class A common stock under employee equity plans		59																								59
Cash dividends declared and paid, at a quarterly amount per Class A share		(809)																										(809)
Repurchase of class A common stock (in shares)								(19)									(19)
Repurchase of class A common stock		(4,104)						$ (4,104)																		(209)		(3,895)
Ending balance (in shares) at Dec. 31, 2021											0				2	3	1,661				245	10
Ending balance at Dec. 31, 2021		36,194							2,995						$ 1,045	$ 1,520									(111)	18,776		14,606		(72)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adoption of new accounting standards		$ 36,194							$ 2,995						$ 1,045	$ 1,520									$ (111)	$ 18,776		$ 14,606		$ (72)

[1] Increase, decrease or balance is less than one million shares.