Supplemental equity information - Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	9 Months Ended
Sep. 30, 2020	Sep. 29, 2019
Accumulated Other Comprehensive Income (Loss), Net of Tax
Beginning balance	$ 981,356	$ 717,223
Other comprehensive income (loss) before reclassifications	(14,583)	0
Amounts reclassified from accumulated other comprehensive loss	(30)	(90)
Net current period other comprehensive income (loss), net of taxes	(14,613)	(90)
Ending balance	426,129	625,458
Total
Accumulated Other Comprehensive Income (Loss), Net of Tax
Beginning balance	8,202	(6,881)
Ending balance	(6,411)	(6,971)
Retirement Plans
Accumulated Other Comprehensive Income (Loss), Net of Tax
Beginning balance	936	(6,881)
Other comprehensive income (loss) before reclassifications	(5,675)	0
Amounts reclassified from accumulated other comprehensive loss	(30)	(90)
Net current period other comprehensive income (loss), net of taxes	(5,705)	(90)
Ending balance	(4,769)	(6,971)
Foreign Currency Translation
Accumulated Other Comprehensive Income (Loss), Net of Tax
Beginning balance	7,266	0
Other comprehensive income (loss) before reclassifications	(8,908)	0
Amounts reclassified from accumulated other comprehensive loss	0	0
Net current period other comprehensive income (loss), net of taxes	(8,908)	0
Ending balance	$ (1,642)	$ 0

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

No definition available.

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Amount after tax, before reclassification adjustments, of other comprehensive income (loss), attributable to parent.

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Amount after tax of other comprehensive income (loss) attributable to parent entity.

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Amount after tax of reclassification adjustments of other comprehensive income (loss) attributable to parent.

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Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity.

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