Stock-based compensation - Schedule of PU activity (Detail)	12 Months Ended
	Dec. 31, 2021 $ / shares shares	Dec. 31, 2020 $ / shares shares	Dec. 31, 2019 $ / shares shares
Weighted Average Grant Date Fair Value
Outstanding weighted average grant date fair value, beginning balance | $ / shares	$ 34.56
Outstanding weighted average grant date fair value, ending balance | $ / shares		$ 34.56
Maximum shares eligible to receive
Outstanding maximum shares eligible to receive, beginning balance	4,876,196	6,058,464
Outstanding maximum shares eligible to receive, ending balance		4,876,196	6,058,464
Performance Units
Number of Performance Units
Outstanding number of shares (Units), beginning balance	4,876,196	6,058,464	3,712,402
Granted, number of shares (Units)	1,340,877	1,253,766	1,579,109
Vested, number of shares (Units)	(1,784,140)	(1,496,377)	(3,276)
Forfeited, number of shares (Units)	(258,258)	(539,670)	(248,031)
Adjustment upon final determination of level of performance goal achievement	408,480	(399,987)	1,018,260
Outstanding number of shares (Units), ending balance	4,583,155	4,876,196	6,058,464
Expected to vest, number of shares (Units)	4,263,803	4,573,356	5,507,640
Weighted Average Grant Date Fair Value
Outstanding weighted average grant date fair value, beginning balance | $ / shares	$ 34.56	$ 31.07	$ 28.40
Granted, weighted average grant date fair value | $ / shares	44.06	42.49	34.68
Vested, weighted average grant date fair value | $ / shares	30.66	25.21	27.47
Forfeited, weighted average grant date fair value | $ / shares	39.97	33.77	29.04
Adjustment upon final determination of level of performance goal achievement | $ / shares	43.99	42.60	34.72
Outstanding weighted average grant date fair value, ending balance | $ / shares	$ 39.40	$ 34.56	$ 31.07
Maximum shares eligible to receive
Outstanding maximum shares eligible to receive, beginning balance	4,876,196	6,058,464	3,712,402
Granted, maximum shares eligible to receive	2,681,754	2,507,532	3,158,218
Vested, maximum shares eligible to receive	(1,784,140)	(1,496,377)	(3,276)
Forfeited, maximum shares eligible to receive	(320,098)	(560,867)	(278,755)
Adjustment upon final determination of level of performance goal achievement	(870,557)	(1,632,556)	(530,125)
Outstanding maximum shares eligible to receive, ending balance	4,583,155	4,876,196	6,058,464
Net settlement on vesting of performance units (Note 18) (in shares)	1,102,440	902,532	2,151
Increase due to achievement of higher-than-target performance (in percentage)	31.20%		66.67%
Decrease due to achievement of lower-than-target performance (in percentage)		0.3298