Employee benefit plans - Plans' Obligation and Assets (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Change in Plan Assets
Fair value of plan assets at January 1	$ 1,813,135
Fair value of plan assets at December 31	431,047	$ 1,813,135
Retirement Plans
Change in Benefit Obligation
Benefit obligation at January 1	2,092,297	1,976,197
Service cost	3,916	3,969	$ 3,968
Interest cost	24,186	51,297	57,348
Plan participant contributions	14	165
Plan amendments	608	419
Actuarial (gain)/loss	(138,157)	149,264
Benefits paid	(66,641)	(96,257)
Impact of foreign exchange rates	(4,999)	13,482
Effect of settlements	(1,396,494)	(2,463)
Effect of curtailments	(97)	(3,776)
Benefit obligation at December 31	514,633	2,092,297	1,976,197
Change in Plan Assets
Fair value of plan assets at January 1	1,799,109	1,683,520
Actual return on plan assets	(46,148)	188,695
Company contributions	140,226	17,282
Plan participant contributions	14	165
Benefits paid	(66,641)	(96,257)
Impact of foreign exchange rates	(4,630)	13,667
Effect of settlements	(1,396,494)	(2,752)
Expenses paid	(8,331)	(5,211)
Fair value of plan assets at December 31	417,105	1,799,109	1,683,520
Funded Status of the Plans	(97,528)	(293,188)
Retiree Health and Life Insurance Plans
Change in Benefit Obligation
Benefit obligation at January 1	14,880	14,495
Service cost	374	358	308
Interest cost	197	336	467
Plan participant contributions	0	443
Plan amendments	0	0
Actuarial (gain)/loss	(939)	356
Benefits paid	(768)	(1,122)
Impact of foreign exchange rates	1	14
Effect of settlements	0	0
Effect of curtailments	0	0
Benefit obligation at December 31	13,745	14,880	14,495
Change in Plan Assets
Fair value of plan assets at January 1	14,026	12,881
Actual return on plan assets	(84)	1,372
Company contributions	768	626
Plan participant contributions	0	443
Benefits paid	(768)	(1,122)
Impact of foreign exchange rates	0	0
Effect of settlements	0	0
Expenses paid	0	(174)
Fair value of plan assets at December 31	13,942	14,026	$ 12,881
Funded Status of the Plans	$ 197	$ (854)

Amount of increase (decrease) in plan assets of defined benefit plan from actual return (loss) determined by change in fair value of plan assets adjusted for contributions, benefit payments, and other expenses.

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Amount of gain (loss) from change in actuarial assumptions which (increases) decreases benefit obligation of defined benefit plan. Assumptions include, but are not limited to, interest, mortality, employee turnover, salary, and temporary deviation from substantive plan.

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Amount of administration expense of defined benefit plan which decreases plan assets. Excludes plan administration expense paid by employer.

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Amount of actuarial present value of benefits attributed to service rendered by employee for defined benefit plan.

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Amount of payment to participant of defined benefit plan which decreases benefit obligation. For pension plan, payment includes, but is not limited to, pension benefits and death benefits. For other postretirement plan, payment includes, but is not limited to, prescription drug benefits, health care benefits, life insurance benefits, and legal, educational and advisory services.

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Amount of contributions received by defined benefit plan from participant which increase benefit obligation.

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Amount of payment, which decreases benefit obligation of defined benefit plan, for irrevocable action relieving primary responsibility for benefit obligation and eliminating risk for obligation and assets used to effect settlement. Transaction constituting settlement includes, but is not limited to, making lump-sum cash payment to participant in exchange for their rights to receive specified benefits and purchasing nonparticipating annuity contract. Excludes decreases to benefit obligation for remeasurement due to settlement.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount of contribution received by defined benefit plan from employer which increases plan assets.

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Amount of (increase) decrease in benefit obligation of defined benefit plan from event reducing expected years of future service of present employees or eliminating accrual of benefits for some or all future services of present employees.

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Amount of asset segregated and restricted to provide benefit under defined benefit plan. Asset includes, but is not limited to, stock, bond, other investment, earning from investment, and contribution by employer and employee.

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Amount of foreign currency translation gain (loss) which (increases) decreases benefit obligation of defined benefit plan.

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Amount of funded (unfunded) status of defined benefit plan, measured as difference between fair value of plan assets and benefit obligation. Includes, but is not limited to, overfunded (underfunded) status.

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Amount of cost recognized for passage of time related to defined benefit plan.

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Amount of increase (decrease) in benefit obligation of defined benefit plan from change in terms of existing plan or initiation of new plan.

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Amount of payment to participant under defined benefit plan which decreases plan assets. For pension plan, payment includes, but is not limited to, pension benefits and death benefits. For other postretirement plan, payment includes, but is not limited to, prescription drug benefits, health care benefits, life insurance benefits, and legal, educational and advisory services.

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Amount of contributions received by defined benefit plan from participant which increases plan assets.

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Amount of foreign currency translation gain (loss) which increases (decreases) plan assets of defined benefit plan.

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Amount of cost for actuarial present value of benefits attributed to service rendered by employee for defined benefit plan.

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Amount of payment, which decreases plan assets of defined benefit plan, for irrevocable action relieving primary responsibility for benefit obligation and eliminating risk for obligation and assets used to effect settlement. Transaction constituting settlement includes, but is not limited to, making lump-sum cash payment to participant in exchange for their rights to receive specified benefits and purchasing nonparticipating annuity contract.

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