Disclosure - Restructuring (Additional Information) (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 28, 2025	Jun. 29, 2024	Jun. 28, 2025	Jun. 29, 2024
Restructuring Charges [Abstract]
Restructuring cost in cost of goods sold	$ (16,191)	$ (703)	$ (19,826)	$ (1,491)
RestructuringCost	(22,415)	(1,324)	(27,173)	(2,370)
Restructuring costs in operating expenses	$ (6,224)	$ (621)	$ (7,347)	$ (879)

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