CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS’ EQUITY (Unaudited) - 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)
Balance (in shares) at Dec. 31, 2019			1,197	429
Beginning balance at Dec. 31, 2019	$ 12,805	$ (3)	$ 0	$ (5,563)	$ 11,174	$ 7,813	$ (3)	$ (619)
Components of comprehensive income:
Net income	505					505
Other comprehensive income (loss)	(9)							(9)
Issuance of common stock pursuant to employee stock options (in shares)			1
Issuance of common stock pursuant to employee stock options	27				27
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	(31)				(31)
Share-based compensation expense related to employee stock options and restricted stock units	43				43
Dividends	(316)					(316)
Balance (in shares) at Mar. 31, 2020			1,199	429
Ending balance at Mar. 31, 2020	$ 13,021		$ 0	$ (5,563)	11,213	7,999		(628)
Components of comprehensive income:
Accounting Standards Update [Extensible Enumeration]	Accounting Standards Update 2016-13 [Member]
Balance (in shares) at Dec. 31, 2019			1,197	429
Beginning balance at Dec. 31, 2019	$ 12,805	$ (3)	$ 0	$ (5,563)	11,174	7,813	$ (3)	(619)
Components of comprehensive income:
Net income	1,688
Other comprehensive income (loss)	(14)
Balance (in shares) at Sep. 30, 2020			1,201	429
Ending balance at Sep. 30, 2020	14,382		$ 0	$ (5,563)	11,395	9,183		(633)
Balance (in shares) at Mar. 31, 2020			1,199	429
Beginning balance at Mar. 31, 2020	13,021		$ 0	$ (5,563)	11,213	7,999		(628)
Components of comprehensive income:
Net income	580					580
Other comprehensive income (loss)	(6)							(6)
Issuance of common stock pursuant to employee stock options (in shares)			1
Issuance of common stock pursuant to employee stock options	44				44
Restricted stock surrendered for employees’ tax liability	(3)				(3)
Share-based compensation expense related to employee stock options and restricted stock units	46				46
Balance (in shares) at Jun. 30, 2020			1,200	429
Ending balance at Jun. 30, 2020	13,682		$ 0	$ (5,563)	11,300	8,579		(634)
Components of comprehensive income:
Net income	604					604
Other comprehensive income (loss)	1							1
Issuance of common stock pursuant to employee stock options (in shares)			1
Issuance of common stock pursuant to employee stock options	43				43
Restricted stock surrendered for employees’ tax liability	(6)				(6)
Share-based compensation expense related to employee stock options and restricted stock units	58				58
Balance (in shares) at Sep. 30, 2020			1,201	429
Ending balance at Sep. 30, 2020	14,382		$ 0	$ (5,563)	11,395	9,183		(633)
Balance (in shares) at Dec. 31, 2020			1,203	429
Beginning balance at Dec. 31, 2020	15,037		$ 0	$ (5,563)	11,531	9,691		(622)
Components of comprehensive income:
Net income	619					619
Other comprehensive income (loss)	22							22
Issuance of common stock pursuant to employee stock options (in shares)			1
Issuance of common stock pursuant to employee stock options	33				33
Issuance of common stock pursuant to restricted stock units (in shares)			4
Issuance of common stock pursuant to restricted stock units	0
Restricted stock surrendered for employees' tax liability (in shares)			(2)
Restricted stock surrendered for employees’ tax liability	(165)				(165)
Share-based compensation expense related to employee stock options and restricted stock units	150				150
Dividends	(365)					(365)
Balance (in shares) at Mar. 31, 2021			1,206	429
Ending balance at Mar. 31, 2021	15,331		$ 0	$ (5,563)	11,549	9,945		(600)
Balance (in shares) at Dec. 31, 2020			1,203	429
Beginning balance at Dec. 31, 2020	15,037		$ 0	$ (5,563)	11,531	9,691		(622)
Components of comprehensive income:
Net income	2,135
Other comprehensive income (loss)	35
Balance (in shares) at Sep. 30, 2021			1,207	429
Ending balance at Sep. 30, 2021	16,950		$ 0	$ (5,563)	11,640	11,460		(587)
Balance (in shares) at Mar. 31, 2021			1,206	429
Beginning balance at Mar. 31, 2021	15,331		$ 0	$ (5,563)	11,549	9,945		(600)
Components of comprehensive income:
Net income	876					876
Other comprehensive income (loss)	7							7
Issuance of common stock pursuant to employee stock options	33				33
Restricted stock surrendered for employees’ tax liability	(7)				(7)
Share-based compensation expense related to employee stock options and restricted stock units	46				46
Balance (in shares) at Jun. 30, 2021			1,206	429
Ending balance at Jun. 30, 2021	16,286		$ 0	$ (5,563)	11,621	10,821		(593)
Components of comprehensive income:
Net income	639					639
Other comprehensive income (loss)	6							6
Issuance of common stock pursuant to employee stock options (in shares)			0
Issuance of common stock pursuant to employee stock options	12				12
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	(73)				(73)
Share-based compensation expense related to employee stock options and restricted stock units	80				80
Balance (in shares) at Sep. 30, 2021			1,207	429
Ending balance at Sep. 30, 2021	$ 16,950		$ 0	$ (5,563)	$ 11,640	$ 11,460		$ (587)