Stockholders' Equity - Changes in Stockholders Equity (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Changes in Stockholders' Equity
Beginning balance	$ 236,447	$ 168,602	$ 201,875	$ 146,043	$ 201,875	$ 146,043	$ 182,973
Other comprehensive income (loss)	2,075	(1,323)			1,122	(516)
Net income	15,328	9,879			39,244	19,801	49,868	$ 20,079
Ending balance	259,151	182,973	236,447	168,602	259,151	182,973	259,151	182,973
Common stock
Changes in Stockholders' Equity
Beginning balance	110	108	109	108	109	108	108
Stock-based compensation and issuance of employee benefit plan stock	0	0			1	0
Ending balance	110	108	110	108	110	108	110	108
Treasury stock
Changes in Stockholders' Equity
Beginning balance	(7,837)	(7,837)	(7,837)	(7,837)	(7,837)	(7,837)	(7,837)
Ending balance	(7,837)	(7,837)	(7,837)	(7,837)	(7,837)	(7,837)	(7,837)	(7,837)
Additional paid-in capital
Changes in Stockholders' Equity
Beginning balance	110,633	86,896	99,025	75,066	99,025	75,066	92,711
Stock-based compensation and issuance of employee benefit plan stock	5,301	5,815			16,909	17,645
Ending balance	115,934	92,711	110,633	86,896	115,934	92,711	115,934	92,711
Accumulated other comprehensive income (loss)
Changes in Stockholders' Equity
Beginning balance	(3,993)	(3,680)	(3,040)	(4,487)	(3,040)	(4,487)	(5,003)
Other comprehensive income (loss)	2,075	(1,323)			1,122	(516)
Ending balance	(1,918)	(5,003)	(3,993)	(3,680)	(1,918)	(5,003)	(1,918)	(5,003)
Retained earnings
Changes in Stockholders' Equity
Beginning balance	137,534	93,115	113,618	83,193	113,618	83,193	102,994
Net income	15,328	9,879			39,244	19,801
Ending balance	$ 152,862	$ 102,994	$ 137,534	$ 93,115	$ 152,862	$ 102,994	$ 152,862	$ 102,994