Pension and other postretirement benefits - Expected benefit payments (Detail) $ in Thousands	Dec. 31, 2020 USD ($)
Pension
Schedule Of Pension Expected Future Benefit Payments [Line Items]
2021	$ 22,527
2022	22,997
2023	23,433
2024	24,018
2025	24,354
Years 2026 — 2030	128,246
Other Benefits
Schedule Of Pension Expected Future Benefit Payments [Line Items]
2021	3,123
2022	2,996
2023	2,864
2024	2,583
2025	2,481
Years 2026 — 2030	$ 8,622

Schedule of Pension Expected Future Benefit Payments [Line Items]

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- Definition

Amount of benefit for defined benefit plan expected to be paid in five fiscal years after fifth fiscal year following current fiscal year.

+ 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 (f)
-URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920

+ Details

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- Definition

Amount of benefit for defined benefit plan expected to be paid in next fiscal year following current fiscal year.

+ References

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Amount of benefit for defined benefit plan expected to be paid in fifth fiscal year following current fiscal year.

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Amount of benefit for defined benefit plan expected to be paid in fourth fiscal year following current fiscal year.

+ References

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Amount of benefit for defined benefit plan expected to be paid in third fiscal year following current fiscal year.

+ References

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Amount of benefit for defined benefit plan expected to be paid in second fiscal year following current fiscal year.

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