Shareholders' equity - Restricted Stock and RSU Awards (Detail) - Restricted Stock and Restricted Stock Units - $ / shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Shares
Unvested at beginning of year (in shares)	2,614,654,000	2,132,936,000	1,567,704,000
Granted (in shares)	1,282,636,000	1,416,300,000	1,356,848,000
Settled (in shares)	(899,282,000)	(738,159,000)	(581,479,000)
Canceled (in shares)	(155,720,000)	(196,423,000)	(210,137,000)
Unvested at end of year (in shares)	2,842,288,000	2,614,654,000	2,132,936,000
Weighted average fair value
Unvested at beginning of year (in dollars per share)	$ 13.09	$ 13.22	$ 14.65
Granted (in dollars per share)	17.83	13.39	13.09
Settled (in dollars per share)	13.21	14.03	16.31
Canceled (in dollars per share)	14.56	13.14	14.53
Unvested at end of year (in dollars per share)	$ 15.11	$ 13.09	$ 13.22