Employee benefit plans - Accumulated Other Comprehensive Loss/(Income) Expects to Recognize as Components of Net Periodic Benefit Cost (Details) $ in Thousands	Dec. 31, 2019 USD ($)
Retirement Plan
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss/(gain)	$ 22,486
Prior service cost/(credit)	1,037
Expected amortization of defined benefit plan amounts from AOCI in next fiscal year	23,523
Retiree Health and Life Insurance Plans
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss/(gain)	(808)
Prior service cost/(credit)	(279)
Expected amortization of defined benefit plan amounts from AOCI in next fiscal year	$ (1,087)

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.

No definition available.

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- Definition

Amount of cost (credit) included in accumulated other comprehensive (income) loss expected to be recognized in net periodic benefit cost (credit) for fiscal year following most recent annual statement of financial position.

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

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- Definition

Amount included in accumulated other comprehensive income (loss) for gain (loss) of defined benefit plan expected to be recognized in net periodic benefit (cost) credit for fiscal year following most recent annual statement of financial position.

+ References

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- Definition

Amount included in accumulated other comprehensive (income) loss for prior service cost (credit) expected to be recognized in net periodic benefit cost (credit) for fiscal year following most recent annual statement of financial position.

+ References

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