Other current liabilities - Other Current Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Sep. 27, 2020	Jun. 28, 2020	Mar. 29, 2020	Dec. 31, 2019
Other Liabilities Disclosure [Abstract]
Reserves	$ 13,617				$ 11,659
Accrued foreign taxes	13,227				6,053
Accrued losses on contracts	11,455				11,352
Other	6,738				1,829
Other current liabilities	$ 45,037	$ 31,528	$ 31,457	$ 32,703	$ 30,893

Amount of liabilities classified as other, due within one year or the normal operating cycle, if longer.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=121566466&loc=d3e6904-107765

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section 45
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=121566466&loc=d3e6911-107765

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.20)
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

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