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Employee benefit plans - Amounts Recognized in Other Comprehensive Loss/(Income) (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2022 | Dec. 31, 2021 | Dec. 31, 2020
Retirement Plans |  |  |
Adjustments arising during the period: |  |  |
Net actuarial loss/(gain) | $ 4,839 | $ (63,684) | $ 12,452
Prior service cost/(credit) | 678 | 837 | 1,229
Net settlements/curtailments | (522) | (550,706) | (886)
Amortization recognized during the period: |  |  |
Net actuarial (loss)/gain | (6,240) | (16,503) | (28,833)
Prior service (cost)/credit | (913) | (900) | (1,006)
Total recognized in other comprehensive loss/(income) | (2,158) | (630,956) | (17,044)
Total recognized in net periodic benefit cost and other comprehensive loss/(income) | 9,081 | (57,633) | 18,214
Retiree Health and Life Insurance Plans |  |  |
Adjustments arising during the period: |  |  |
Net actuarial loss/(gain) | (761) | (412) | (468)
Prior service cost/(credit) | 0 | 0 | 0
Net settlements/curtailments | 0 | 0 | 0
Amortization recognized during the period: |  |  |
Net actuarial (loss)/gain | 681 | 744 | 834
Prior service (cost)/credit | 0 | 0 | 279
Total recognized in other comprehensive loss/(income) | (80) | 332 | 645
Total recognized in net periodic benefit cost and other comprehensive loss/(income) | $ (622) | $ (285) | $ (145)

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- Definition Projected defined benefit plan amortization of gains losses. + References No definition available. + Details
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- Definition Projected defined benefit plan amortization of prior service cost credit. + References No definition available. + Details
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- Definition Amount recognized in net periodic benefit cost (credit) and other comprehensive (income) loss. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 17 -URI https://asc.fasb.org/extlink&oid=123450688&loc=d3e4179-114921 + Details
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- Definition Amount, before tax, after reclassification adjustment, of increase (decrease) in accumulated other comprehensive income from gain (loss) of defined benefit plan. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 11 -URI https://asc.fasb.org/extlink&oid=126968391&loc=d3e637-108580 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 10A -Subparagraph (i) -URI https://asc.fasb.org/extlink&oid=126968391&loc=SL7669646-108580 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (i) -URI https://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 + Details
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- Definition Amount of gain (loss) recognized in net periodic benefit (cost) credit from settlement and curtailment. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 6 -Subparagraph (a)(7) -URI https://asc.fasb.org/extlink&oid=123447040&loc=d3e2709-114920 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(7) -URI https://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 45 -Paragraph 3A -URI https://asc.fasb.org/extlink&oid=123453770&loc=SL108413299-114919 + Details
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- Definition Amount, before tax, of cost (credit) of benefit change attributable to participants' prior service from plan amendment or plan initiation of defined benefit plan, that has not been recognized in net periodic benefit cost (credit). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (i) -URI https://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 10A -Subparagraph (j) -URI https://asc.fasb.org/extlink&oid=126968391&loc=SL7669646-108580 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 11 -URI https://asc.fasb.org/extlink&oid=126968391&loc=d3e637-108580 + Details
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