Stockholders' Equity - Changes in Stockholders Equity (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Changes in Stockholders' Equity
Beginning balance	$ 103,320	$ 65,272	$ 93,404	$ 62,060	$ 73,728
Other comprehensive income (loss)	141	608	(345)	(469)
Net Income	7,778	5,243	15,885	7,778	29,438	$ 13,180
Ending balance	114,803	73,728	114,803	73,728	114,803	73,728
Common stock
Changes in Stockholders' Equity
Beginning balance	5	5	5	5	5
Ending balance	5	5	5	5	5	5
Treasury stock
Changes in Stockholders' Equity
Beginning balance	(1,837)	(1,837)	(1,837)	(1,837)	(1,837)
Ending balance	(1,837)	(1,837)	(1,837)	(1,837)	(1,837)	(1,837)
Additional paid-in capital
Changes in Stockholders' Equity
Beginning balance	45,160	35,412	42,865	33,658	38,017
Stock-based compensation and issuance of employee benefit plan stock	3,564	2,605	5,859	4,359
Ending balance	48,724	38,017	48,724	38,017	48,724	38,017
Accumulated other comprehensive income (loss)
Changes in Stockholders' Equity
Beginning balance	(666)	(2,063)	(180)	(986)	(1,455)
Other comprehensive income (loss)	141	608	(345)	(469)
Ending balance	(525)	(1,455)	(525)	(1,455)	(525)	(1,455)
Retained earnings
Changes in Stockholders' Equity
Beginning balance	60,658	33,755	52,551	31,220	38,998
Net Income	7,778	5,243	15,885	7,778
Ending balance	$ 68,436	$ 38,998	$ 68,436	$ 38,998	$ 68,436	$ 38,998