Income taxes - Pre-tax Net Loss and Income Tax (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2020	Sep. 29, 2019	Sep. 30, 2020	Sep. 29, 2019
Income Tax Disclosure [Abstract]
Pre-tax net income (loss)	$ (28,350)	$ (11,742)	$ (572,085)	$ (20,779)
Income tax expense (benefit)	$ 3,098	$ 7,226	$ (22,200)	$ 4,929
Effective tax rate (percent)			3.90%

Amount of income (loss) from continuing operations, including income (loss) from equity method investments, before deduction of income tax expense (benefit), and income (loss) attributable to noncontrolling interest.

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+ Details

- Definition

Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

+ References + Details