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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, 2021 | Dec. 31, 2020 | Dec. 31, 2019
Retirement Plans |  |  |
Adjustments arising during the period: |  |  |
Net actuarial loss/(gain) | $ (63,684) | $ 12,452 | $ 146,414
Prior service cost/(credit) | 837 | 1,229 | 1,667
Net settlements/curtailments | (550,706) | (886) | (2,377)
Reversal of amortization: |  |  |
Net actuarial (loss)/gain | (16,503) | (28,833) | (30,681)
Prior service (cost)/credit | (900) | (1,006) | (1,022)
Total recognized in other comprehensive loss/(income) | (630,956) | (17,044) | 114,001
Total recognized in net periodic benefit cost and other comprehensive loss/(income) | (57,633) | 18,214 | 144,254
Retiree Health and Life Insurance Plans |  |  |
Adjustments arising during the period: |  |  |
Net actuarial loss/(gain) | (412) | (468) | (914)
Prior service cost/(credit) | 0 | 0 | 0
Net settlements/curtailments | 0 | 0 | 0
Reversal of amortization: |  |  |
Net actuarial (loss)/gain | 744 | 834 | 823
Prior service (cost)/credit | 0 | 279 | 498
Total recognized in other comprehensive loss/(income) | 332 | 645 | 407
Total recognized in net periodic benefit cost and other comprehensive loss/(income) | $ (285) | $ (145) | $ (857)

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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 http://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 http://asc.fasb.org/extlink&oid=124509347&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 http://asc.fasb.org/extlink&oid=124509347&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 http://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 http://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 http://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 http://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 http://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 http://asc.fasb.org/extlink&oid=124509347&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 http://asc.fasb.org/extlink&oid=124509347&loc=d3e637-108580 + Details
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