Disclosure - Restructuring (Additional Information) (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jul. 01, 2023	Jul. 01, 2023
Restructuring Charges [Abstract]
Restructuring cost in cost of goods sold	$ 0	$ 2,279
Restructuring costs in operating expenses	$ 1,192	$ 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