Stockholders' Equity - Changes in Stockholders Equity (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Jul. 01, 2019	Jun. 30, 2019	Jan. 01, 2019	Dec. 31, 2018	Jul. 01, 2018	Jun. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
Stockholders' equity	$ 56,508	$ 39,125	$ 56,508	$ 39,125	$ 56,508	$ 39,125		$ 53,061		$ 43,549		$ 34,995		$ 27,709
Other comprehensive income (loss)	(469)	(100)	(394)	(550)
Net Income	2,134	2,883	8,320	7,046	11,347	8,902
Common stock
Stockholders' equity	5	5	5	5	5	5		5		5		5		5
Treasury stock
Stockholders' equity	(1,837)	(1,837)	(1,837)	(1,837)	(1,837)	(1,837)		(1,837)		(1,837)		(1,837)		(1,837)
Additional paid-in capital
Stockholders' equity	31,817	25,375	31,817	25,375	31,817	25,375		30,035		26,791		24,028		21,389
Stock-based compensation and issuance of employee benefit plan stock	1,782	1,347	5,026	3,986
Accumulated other comprehensive income (loss)
Stockholders' equity	(1,429)	(1,034)	(1,429)	(1,034)	(1,429)	(1,034)		(960)		(1,035)		(934)		(484)
Other comprehensive income (loss)	(469)	(100)	(394)	(550)
Retained earnings
Stockholders' equity	27,952	16,616	27,952	16,616	$ 27,952	$ 16,616		$ 25,818		$ 19,625		$ 13,733		$ 8,636
Cumulative effect of changes in accounting principles							$ 0		$ 7		$ 0		$ 934
Net Income	$ 2,134	$ 2,883	$ 8,320	$ 7,046