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Fair value measurements - Assets and Liabilities Measured on Recurring Basis (Details) - USD ($) $ in Thousands | Dec. 31, 2023 | Dec. 31, 2022
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total postretirement benefit plan assets | $ 308,800 | $ 265,875
Common Collective |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total postretirement benefit plan assets | 12,958 | 6,497
Mutual funds |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total postretirement benefit plan assets | 45,931 | 50,467
Fixed income securities |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total postretirement benefit plan assets | 242,702 | 198,628
Short-term investments |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total postretirement benefit plan assets | 4,175 | 1,099
Real estate funds |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total postretirement benefit plan assets | 400 | 680
Cash and accrued income |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total postretirement benefit plan assets | 2,634 | 8,504
Assets measured at NAV |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total postretirement benefit plan assets | 77,207 | 40,104
Assets measured at NAV | Common Collective |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total postretirement benefit plan assets | 12,958 | 6,497
Assets measured at NAV | Mutual funds |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total postretirement benefit plan assets | 0 | 0
Assets measured at NAV | Fixed income securities |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total postretirement benefit plan assets | 63,849 | 32,927
Assets measured at NAV | Short-term investments |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total postretirement benefit plan assets | 0 | 0
Assets measured at NAV | Real estate funds |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total postretirement benefit plan assets | 400 | 680
Assets measured at NAV | Cash and accrued income |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total postretirement benefit plan assets | 0 | 0
Level 1 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total postretirement benefit plan assets | 2,634 | 8,504
Level 1 | Common Collective |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total postretirement benefit plan assets | 0 | 0
Level 1 | Mutual funds |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total postretirement benefit plan assets | 0 | 0
Level 1 | Fixed income securities |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total postretirement benefit plan assets | 0 | 0
Level 1 | Short-term investments |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total postretirement benefit plan assets | 0 | 0
Level 1 | Real estate funds |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total postretirement benefit plan assets | 0 | 0
Level 1 | Cash and accrued income |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total postretirement benefit plan assets | 2,634 | 8,504
Level 2 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total postretirement benefit plan assets | 228,959 | 217,267
Level 2 | Common Collective |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total postretirement benefit plan assets | 0 | 0
Level 2 | Mutual funds |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total postretirement benefit plan assets | 45,931 | 50,467
Level 2 | Fixed income securities |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total postretirement benefit plan assets | 178,853 | 165,701
Level 2 | Short-term investments |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total postretirement benefit plan assets | 4,175 | 1,099
Level 2 | Real estate funds |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total postretirement benefit plan assets | 0 | 0
Level 2 | Cash and accrued income |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total postretirement benefit plan assets | 0 | 0
Level 3 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total postretirement benefit plan assets | 0 | 0
Level 3 | Common Collective |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total postretirement benefit plan assets | 0 | 0
Level 3 | Mutual funds |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total postretirement benefit plan assets | 0 | 0
Level 3 | Fixed income securities |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total postretirement benefit plan assets | 0 | 0
Level 3 | Short-term investments |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total postretirement benefit plan assets | 0 | 0
Level 3 | Real estate funds |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total postretirement benefit plan assets | 0 | 0
Level 3 | Cash and accrued income |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total postretirement benefit plan assets | 0 | 0
Fair Value, Recurring | Hedge derivatives, net: | Net investment hedge |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Net position of derivative | (5,073) |
Fair Value, Recurring | Hedge derivatives, net: | Assets measured at NAV | Net investment hedge |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Net position of derivative | 0 |
Fair Value, Recurring | Hedge derivatives, net: | Level 1 | Net investment hedge |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Net position of derivative | 0 |
Fair Value, Recurring | Hedge derivatives, net: | Level 2 | Net investment hedge |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Net position of derivative | (5,073) |
Fair Value, Recurring | Hedge derivatives, net: | Level 3 | Net investment hedge |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Net position of derivative | 0 |
Commodity Contracts | Fair Value, Recurring | Hedge derivatives, net: |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Net position of derivative | (41) | (172)
Commodity Contracts | Fair Value, Recurring | Hedge derivatives, net: | Assets measured at NAV |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Net position of derivative | 0 | 0
Commodity Contracts | Fair Value, Recurring | Hedge derivatives, net: | Level 1 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Net position of derivative | 0 | 0
Commodity Contracts | Fair Value, Recurring | Hedge derivatives, net: | Level 2 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Net position of derivative | (41) | (172)
Commodity Contracts | Fair Value, Recurring | Hedge derivatives, net: | Level 3 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Net position of derivative | 0 | 0
Commodity Contracts | Fair Value, Recurring | Non-hedge derivatives, net: |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Net position of derivative | (6,770) | (8,638)
Commodity Contracts | Fair Value, Recurring | Non-hedge derivatives, net: | Assets measured at NAV |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Net position of derivative | 0 | 0
Commodity Contracts | Fair Value, Recurring | Non-hedge derivatives, net: | Level 1 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Net position of derivative | 0 | 0
Commodity Contracts | Fair Value, Recurring | Non-hedge derivatives, net: | Level 2 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Net position of derivative | (6,770) | (8,638)
Commodity Contracts | Fair Value, Recurring | Non-hedge derivatives, net: | Level 3 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Net position of derivative | 0 | 0
Foreign Exchange Contracts | Fair Value, Recurring | Hedge derivatives, net: |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Net position of derivative | 1,502 | (863)
Foreign Exchange Contracts | Fair Value, Recurring | Hedge derivatives, net: | Assets measured at NAV |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Net position of derivative | 0 | 0
Foreign Exchange Contracts | Fair Value, Recurring | Hedge derivatives, net: | Level 1 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Net position of derivative | 0 | 0
Foreign Exchange Contracts | Fair Value, Recurring | Hedge derivatives, net: | Level 2 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Net position of derivative | 1,502 | (863)
Foreign Exchange Contracts | Fair Value, Recurring | Hedge derivatives, net: | Level 3 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Net position of derivative | 0 | 0
Foreign Exchange Contracts | Fair Value, Recurring | Non-hedge derivatives, net: |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Net position of derivative | (29) | (54)
Foreign Exchange Contracts | Fair Value, Recurring | Non-hedge derivatives, net: | Assets measured at NAV |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Net position of derivative | 0 | 0
Foreign Exchange Contracts | Fair Value, Recurring | Non-hedge derivatives, net: | Level 1 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Net position of derivative | 0 | 0
Foreign Exchange Contracts | Fair Value, Recurring | Non-hedge derivatives, net: | Level 2 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Net position of derivative | (29) | (54)
Foreign Exchange Contracts | Fair Value, Recurring | Non-hedge derivatives, net: | Level 3 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Net position of derivative | $ 0 | $ 0

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- Definition 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. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 17 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480482/715-20-55-17 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (d)(iv)(02) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480506/715-20-50-1 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (d)(ii) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480506/715-20-50-1 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (d)(iv)(01) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480506/715-20-50-1 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480506/715-20-50-1 Reference 6: http://www.xbrl.org/2003/role/exampleRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (d)(ii) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480506/715-20-50-1 Reference 7: http://www.xbrl.org/2003/role/exampleRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (d)(iv)(01) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480506/715-20-50-1 + Details
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