Stockholders' equity (Narrative) (Details) $ / shares in Units, shares in Millions, $ in Millions		1 Months Ended							3 Months Ended						9 Months Ended
	Feb. 25, 2022 USD ($) shares	Dec. 30, 2022 $ / shares	Oct. 31, 2022 USD ($) $ / shares	Sep. 30, 2022 USD ($) $ / shares	Aug. 31, 2022 $ / shares	Jun. 30, 2022 $ / shares	Mar. 31, 2022 $ / shares	Dec. 31, 2021 $ / shares	Sep. 30, 2022 USD ($) $ / shares shares	Jun. 30, 2022 USD ($) shares	Mar. 31, 2022 USD ($) $ / shares shares	Sep. 30, 2021 USD ($) $ / shares shares	Jun. 30, 2021 USD ($) shares	Mar. 31, 2021 USD ($) $ / shares shares	Sep. 30, 2022 USD ($) shares	Sep. 30, 2021 USD ($) shares	Feb. 24, 2022 financial_institution
Class of Stock [Line Items]
Stock repurchased (in shares) | shares									1.5	0.0	24.6	4.6	6.5	3.7	26.1	14.8
Stock repurchased									$ 900	$ 0	$ 5,410	$ 1,069	$ 1,592	$ 865	$ 6,310	$ 3,526
Repurchases of common stock									0		$ 6,310	$ 1,069	1,592	$ 865
Amount available for stock repurchases under a board approved stock repurchase plan				$ 4,600					$ 4,600						$ 4,600
Dividends declared per share (in usd per share) | $ / shares					$ 1.94		$ 1.94	$ 1.94	$ 1.94		$ 1.94	$ 1.76		$ 1.76
Dividends paid per share (in usd per share) | $ / shares				$ 1.94		$ 1.94	$ 1.94
Subsequent Event
Class of Stock [Line Items]
Stock repurchase program, additional authorized amount			$ 2,400
Dividends declared per share (in usd per share) | $ / shares			$ 1.94
Accumulated deficit
Class of Stock [Line Items]
Repurchases of common stock									$ 900		$ 5,410	$ 1,069	$ 1,592	$ 865
Common stock and additional paid-in capital
Class of Stock [Line Items]
Repurchases of common stock									$ (900)		$ 900
Accelerated stock repurchase agreement
Class of Stock [Line Items]
Number of Third-Party Financial Institutions | financial_institution																	3
Stock repurchased (in shares) | shares	23.3								1.5						24.8
Stock repurchased	$ 6,000
Accelerated stock repurchase agreement | Accumulated deficit
Class of Stock [Line Items]
Repurchases of common stock	5,100								$ 900
Accelerated stock repurchase agreement | Common stock and additional paid-in capital
Class of Stock [Line Items]
Repurchases of common stock	$ 900
Forecast
Class of Stock [Line Items]
Dividends paid per share (in usd per share) | $ / shares		$ 1.94