Stockholders' equity - Schedule of Changes in Stockholders' Equity (Details) - USD ($) $ in Millions	3 Months Ended						9 Months Ended
	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2022	Sep. 30, 2021
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning			$ 13,333				$ 13,333
Net income	$ 2,295			$ 1,947			6,787	$ 5,631
Other comprehensive income (loss), net of taxes	26			10			3	47
Balance, ending	14,507						14,507
Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning	1,741	$ 1,741	1,741	1,741	$ 1,741	$ 1,741	1,741	1,741
Balance, ending	1,741	1,741	1,741	1,741	1,741	1,741	1,741	1,741
Paid-in Capital
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning	2,783	2,667	2,630	2,485	2,391	2,333	2,630	2,333
Common stock issued for stock-based awards	26	31	(36)	27	25	(3)
Stock compensation	68	85	74	50	69	61
Other			(1)	1
Balance, ending	2,877	2,783	2,667	2,563	2,485	2,391	2,877	2,563
Retained Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning	48,280	47,053	45,919	43,846	42,860	42,051	45,919	42,051
Net income	2,295	2,291	2,201	1,947	1,931	1,753
Dividends declared and paid	(1,051)	(1,060)	(1,063)	(942)	(942)	(940)
Dividend equivalents on RSUs	(5)	(4)	(5)	(3)	(4)	(4)
Other			1	(1)	1
Balance, ending	49,519	48,280	47,053	44,847	43,846	42,860	49,519	44,847
Treasury Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning	(38,532)	(37,291)	(36,800)	(36,596)	(36,479)	(36,578)	(36,800)	(36,578)
Common stock issued for stock-based awards	52	25	93	48	29	199
Stock repurchases	(996)	(1,266)	(584)	(139)	(146)	(100)
Balance, ending	(39,476)	(38,532)	(37,291)	(36,687)	(36,596)	(36,479)	(39,476)	(36,687)
AOCI
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning	(180)	(153)	(157)	(323)	(347)	(360)	(157)	(360)
Other comprehensive income (loss), net of taxes	26	(27)	4	10	24	13
Balance, ending	$ (154)	$ (180)	$ (153)	$ (313)	$ (323)	$ (347)	$ (154)	$ (313)