Commitments and Contingencies - Textual (Details)	3 Months Ended
Mar. 30, 2024 USD ($)
Commitments And Contingencies [Line Items]
Sold receivables amount	$ 3,447,000
Due from unrelated third parties	0
Liabilities recorded for obligations	$ 0
Percentage of maximum borrowing capacity of value of eligible securities	70.00%
Available line of credit	$ 100,000,000
Available interest rate on line of credit	7.10%
Minimum [Member]
Commitments And Contingencies [Line Items]
Warranty period	12 months
Maximum [Member]
Commitments And Contingencies [Line Items]
Warranty period	14 months

Commitments and contingencies line items.

No definition available.

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Namespace Prefix:	onto_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Due from unrelated third Parties.

+ References

No definition available.

+ Details

Name:	onto_DueFromUnrelatedThirdParties
Namespace Prefix:	onto_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Intellectual property indemnification obligation.

+ References

No definition available.

+ Details

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Namespace Prefix:	onto_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Maximum borrowing capacity percentage of eligible securities held at line of credit accessed.

+ References

No definition available.

+ Details

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Namespace Prefix:	onto_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Proceeds from accounts receivable.

+ References

No definition available.

+ Details

Name:	onto_ProceedsFromAccountsReceivable
Namespace Prefix:	onto_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Product warranty accrual warranty period.

+ References

No definition available.

+ Details

Name:	onto_ProductWarrantyAccrualWarrantyPeriod
Namespace Prefix:	onto_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The effective interest rate at the end of the reporting period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1

+ Details

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Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

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Namespace Prefix:
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Balance Type:
Period Type:

- Details

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Namespace Prefix:
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