Disclosure - Restructuring (Additional Information) (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 28, 2024	Sep. 30, 2023	Sep. 28, 2024	Sep. 30, 2023
Restructuring Charges [Abstract]
Restructuring cost in cost of goods sold	$ 1,084	$ 0	$ 2,575	$ 2,279
RestructuringCost	3,251	0	5,621	5,505
Restructuring costs in operating expenses	$ 2,167	$ 0	$ 3,046	$ 3,226

Restructuring cost recored to cost of goods sold for inventory write-downs.

No definition available.

Name:	onto_RestructuringCostInCostOfGoodsSold
Namespace Prefix:	onto_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration