Pension and other postretirement benefits - Summarized information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Pension
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation, beginning of year	$ 501,347	$ 470,236
Service cost	1,467	1,416	$ 2,768
Interest cost	9,272	12,827	16,000
Actuarial (gain) loss	(13,567)	36,726
Currency translation	(1,726)	2,273
Benefits paid	(21,138)	(21,092)
Medicare Part D reimbursement	0	0
Plan amendments	0	47
Administrative costs	(981)	(1,086)
Projected benefit obligation, end of year	474,674	501,347	470,236
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of year	457,626	423,300
Actual return on plan assets	22,124	43,276
Contributions	12,159	12,490
Benefits paid	(21,138)	(21,092)
Administrative costs	(981)	(1,086)
Currency translation	3	738
Fair value of plan assets, end of year	469,793	457,626	423,300
Funded status, end of year	(4,881)	(43,721)
Other Benefits
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation, beginning of year	31,921	40,042
Service cost	0	0	9
Interest cost	418	902	1,391
Actuarial (gain) loss	(2,288)	964
Currency translation	0	0
Benefits paid	(3,303)	(5,448)
Medicare Part D reimbursement	56	119
Plan amendments	0	(4,658)
Administrative costs	0	0
Projected benefit obligation, end of year	26,804	31,921	$ 40,042
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Administrative costs	0	0
Funded status, end of year	$ (26,804)	$ (31,921)