Income taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Property, plant and equipment	$ (97,806)	$ (91,752)
Intangibles	(96,057)	(110,796)
Leases	(75,587)	(79,531)
Gross deferred tax liabilities	(269,450)	(282,079)
Retiree health benefits	2,935	4,065
Foreign loss carryforwards	76,462	81,143
U.S. Federal loss and credit carryforwards	34,700	78,100
Capital loss carryforwards	4,050	3,121
Employee benefits	46,503	47,134
Leases	78,518	84,076
Accrued liabilities and other assets	75,611	69,341
Gross deferred tax assets	318,779	366,980
Valuation allowance on deferred tax assets	(93,992)	(128,435)
Total deferred taxes, net	$ (44,663)	$ (43,534)

Deferred Tax Assets, Leases

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Amount of deferred tax liability attributable to taxable temporary differences.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible capital loss carryforwards.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences and carryforwards.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible domestic operating loss carryforwards. Excludes state and local operating loss carryforwards.

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Amount, before allocation of valuation allowance, of deferred tax asset attributable to deductible temporary differences from employee benefits, classified as other.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from postretirement benefits.

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Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized.

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Amount, after deferred tax asset, of deferred tax liability attributable to taxable differences without jurisdictional netting.

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Amount of deferred tax liability attributable to taxable temporary differences from intangible assets other than goodwill.

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Amount of deferred tax liability attributable to taxable temporary differences from property, plant, and equipment.

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