Stockholders' equity (Details Textual) (Details) - USD ($)		1 Months Ended						3 Months Ended
	Dec. 08, 2020	Oct. 31, 2020	Sep. 30, 2020	Jul. 31, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Mar. 31, 2019
Class of Stock [Line Items]
Stock repurchase program, additional authorized amount							$ 4,000,000,000.0
Amount available for stock repurchases under a board approved stock repurchase plan			$ 4,200,000,000					$ 4,200,000,000
Dividends declared per share (in usd per share)				$ 1.60		$ 1.60	$ 1.60	$ 1.60	$ 1.60	$ 1.45	$ 1.45
Dividends paid per share (in usd per share)			$ 1.60		$ 1.60	$ 1.60
Subsequent Event [Member]
Class of Stock [Line Items]
Dividends declared per share (in usd per share)		$ 1.60
Forecast [Member]
Class of Stock [Line Items]
Dividends paid per share (in usd per share)	$ 1.60