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Employee benefits - Contributions to the benefit plans (Details) $ in Thousands | Dec. 31, 2020 USD ($)
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Pension Plans |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |
Expected employer contributions to the benefit plans during the next year | $ 229
OPEB Plan |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |
Expected employer contributions to the benefit plans during the next year | $ 6,333

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- Definition Amount of contributions expected to be received by defined benefit plan from employer in next fiscal year following latest fiscal year. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (g) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 + Details
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Balance Type: | debit
Period Type: | instant

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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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- Details
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Namespace Prefix: |
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- Details
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Namespace Prefix: |
Data Type: | na
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