CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY - USD ($) shares in Millions, $ in Millions	Total	Cumulative Effect, Period of Adoption, Adjustment	Common Stock	Treasury Stock	Additional Paid-In Capital	Retained Earnings	Retained Earnings Cumulative Effect, Period of Adoption, Adjustment	Accumulated Other Comprehensive Income (Loss)	Accumulated Other Comprehensive Income (Loss) Cumulative Effect, Period of Adoption, Adjustment
Balance (in shares) at Dec. 31, 2017			1,186	429
Beginning balance at Dec. 31, 2017	$ 9,462	$ 91	$ 0	$ (5,563)	$ 10,747	$ 4,916	$ 88	$ (638)	$ 3
Components of comprehensive income:
Net income	1,848					1,848
Other comprehensive income (loss)	34							34
Issuance of common stock pursuant to employee stock options (in shares)			5
Issuance of common stock pursuant to employee stock options	98				98
Issuance of common stock pursuant to restricted stock units (in shares)			2
Issuance of common stock pursuant to restricted stock units	0
Restricted stock surrendered for employees' tax liability (in shares)			(1)
Restricted stock surrendered for employees’ tax liability	(93)				(93)
Share-based compensation expense related to employee stock options and restricted stock units	211				211
Dividends	(259)					(259)
Balance (in shares) at Dec. 31, 2018			1,192	429
Ending balance at Dec. 31, 2018	11,392		$ 0	$ (5,563)	10,963	6,593		(601)
Components of comprehensive income:
Net income	1,503					1,503
Other comprehensive income (loss)	(18)							(18)
Issuance of common stock pursuant to employee stock options (in shares)			4
Issuance of common stock pursuant to employee stock options	105				105
Issuance of common stock pursuant to restricted stock units (in shares)			2
Issuance of common stock pursuant to restricted stock units	0
Restricted stock surrendered for employees' tax liability (in shares)			(1)
Restricted stock surrendered for employees’ tax liability	(58)				(58)
Share-based compensation expense related to employee stock options and restricted stock units	164				164
Dividends	(283)					(283)
Balance (in shares) at Dec. 31, 2019			1,197	429
Ending balance at Dec. 31, 2019	12,805	$ (3)	$ 0	$ (5,563)	11,174	7,813	$ (3)	(619)
Components of comprehensive income:
Net income	2,197					2,197
Other comprehensive income (loss)	(3)							(3)
Issuance of common stock pursuant to employee stock options (in shares)			5
Issuance of common stock pursuant to employee stock options	171				171
Issuance of common stock pursuant to restricted stock units (in shares)			1
Issuance of common stock pursuant to restricted stock units	0
Restricted stock surrendered for employees’ tax liability	(40)				(40)
Share-based compensation expense related to employee stock options and restricted stock units	226				226
Dividends	(316)					(316)
Balance (in shares) at Dec. 31, 2020			1,203	429
Ending balance at Dec. 31, 2020	$ 15,037		$ 0	$ (5,563)	$ 11,531	$ 9,691		$ (622)