Stock-based compensation - Changes in Restricted Stock Units (Details) - RSUs	12 Months Ended
	Dec. 31, 2021 $ / shares shares
Restricted Stock Units Outstanding
Balance at beginning of period (in shares) | shares	1,047,071,000
Granted (in shares) | shares	194,388,000
Vested (in shares) | shares	(710,730,000)
Forfeited (in shares) | shares	(38,409,000)
Balance at end of period (in shares) | shares	492,320,000
Weighted Average Grant Date Fair Value
Balance at beginning of period (in dollars per share) | $ / shares	$ 26.06
Granted (in dollars per share) | $ / shares	43.05
Vested (in dollars per share) | $ / shares	22.99
Forfeited (in dollars per share) | $ / shares	28.96
Balance at end of period (in dollars per share) | $ / shares	$ 36.06