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Pension and postretirement benefits - Employer contribution (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Dec. 31, 2020
Pension Plans
Defined Benefit Plan Disclosure
Employer contribution	$ 171
Expected future employer contribution current year		$ 229
OPEB Plan
Defined Benefit Plan Disclosure
Employer contribution	$ 4,600
Expected future employer contribution current year		$ 6,516

X

- Definition

Amount of contribution received by defined benefit plan from employer which increases plan assets.

+ References

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-Publisher FASB
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- Definition

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+ References

No definition available.

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- Definition

Amount of contributions received and expected to be received by defined benefit plan from employer in current fiscal year.

+ References

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