Stockholders' Equity - Changes in Stockholders Equity (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2021
Changes in Stockholders' Equity
Beginning balance	$ 138,245	$ 93,404	$ 103,320	$ 93,404
Common stock repurchased	(2,700)
Other comprehensive income (loss)	(989)	(486)
Net income (loss)	(3,844)	8,107	21,413		$ 26,903
Ending balance	134,001	103,320	134,001	138,245	103,320
Common stock
Changes in Stockholders' Equity
Beginning balance	5	5	5	5
Ending balance	5	5	5	5	5
Treasury stock
Changes in Stockholders' Equity
Beginning balance	(1,837)	(1,837)	(1,837)	(1,837)
Common stock repurchased	(2,666)	0
Ending balance	(4,503)	(1,837)	(4,503)	(1,837)	(1,837)
Additional paid-in capital
Changes in Stockholders' Equity
Beginning balance	55,538	42,865	45,160	42,865
Stock-based compensation and issuance of employee benefit plan stock	3,255	2,295
Ending balance	58,793	45,160	58,793	55,538	45,160
Accumulated other comprehensive income (loss)
Changes in Stockholders' Equity
Beginning balance	(1,376)	(180)	(666)	(180)
Other comprehensive income (loss)	(989)	(486)
Ending balance	(2,365)	(666)	(2,365)	(1,376)	(666)
Retained earnings
Changes in Stockholders' Equity
Beginning balance	85,915	52,551	60,658	52,551
Net income (loss)	(3,844)	8,107
Ending balance	$ 82,071	$ 60,658	$ 82,071	$ 85,915	$ 60,658