Basis of Presentation and New Accounting Pronouncements (Policies)	9 Months Ended
Sep. 24, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of PresentationThe accompanying condensed consolidated financial information of FormFactor, Inc. is unaudited and has been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) and pursuant to the rules and regulations of the Securities and Exchange Commission (“SEC”). However, such information reflects all adjustments, consisting only of normal recurring adjustments, which are, in the opinion of management, necessary for a fair presentation of the financial position, results of operations and cash flows for the interim periods. The condensed consolidated financial statements included herein should be read in conjunction with the consolidated financial statements and the notes thereto included in our 2021 Annual Report on Form 10-K filed with the SEC on February 18, 2022. The results of operations for the interim periods presented are not necessarily indicative of the results to be expected for the full year.
Fiscal Year	Fiscal Year We operate on a 52/53 week fiscal year, whereby the fiscal year ends on the last Saturday of December. Fiscal 2022 and 2021 contain 53 weeks and 52 weeks, respectively, and the nine months ended September 24, 2022 and September 25, 2021 each contained 39 weeks. Fiscal 2022 will end on December 31, 2022.
New Accounting Pronouncements	New Accounting Pronouncements ASU 2021-08 In October 2021, the FASB issued ASU 2021-08, Business Combinations (Topic 805): Accounting for Contract Assets and Contract Liabilities from Contracts with Customers. The new guidance requires contract assets and contract liabilities acquired in a business combination to be recognized and measured by the acquirer on the acquisition date in accordance with Accounting Standards Codification 606, “Revenue from Contracts with Customers,” as if it had originated the contracts. The Company elected to early adopt on a prospective basis during the second quarter of fiscal 2022. The adoption did not have a material effect on the Company's Consolidated Financial Statements.
Fair Value	Whenever possible, the fair values of our financial assets and liabilities are determined using quoted market prices of identical securities or quoted market prices of similar securities from active markets. The three levels of inputs that may be used to measure fair value are as follows: •Level 1 valuations are obtained from real-time quotes for transactions in active exchange markets involving identical securities; •Level 2 valuations utilize significant observable inputs, such as quoted prices for similar assets or liabilities, quoted prices near the reporting date in markets that are less active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities; and •Level 3 valuations utilize unobservable inputs to the valuation methodology and include our own data about assumptions market participants would use in pricing the asset or liability based on the best information available under the circumstances. We did not have any transfers of assets or liabilities measured at fair value on a recurring basis to or from Level 1, Level 2 or Level 3 during the three and nine months ended September 24, 2022 or the year ended December 25, 2021. The carrying values of Cash, Accounts receivable, net, Restricted cash, Prepaid expenses and other current assets, Accounts payable, and Accrued liabilities approximate fair value due to their short maturities. No changes were made to our valuation techniques during the first nine months of fiscal 2022. Assets and Liabilities Measured at Fair Value on a Non-Recurring BasisWe measure and report our non-financial assets such as Property, plant and equipment, Goodwill and Intangible assets at fair value on a non-recurring basis if we determine these assets to be impaired or in the period when we make a business acquisition.

Basis of Presentation and New Accounting Pronouncements (Policies)

9 Months Ended

Sep. 24, 2022

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Basis of PresentationThe accompanying condensed consolidated financial information of FormFactor, Inc. is unaudited and has been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) and pursuant to the rules and regulations of the Securities and Exchange Commission (“SEC”). However, such information reflects all adjustments, consisting only of normal recurring adjustments, which are, in the opinion of management, necessary for a fair presentation of the financial position, results of operations and cash flows for the interim periods. The condensed consolidated financial statements included herein should be read in conjunction with the consolidated financial statements and the notes thereto included in our 2021 Annual Report on Form 10-K filed with the SEC on February 18, 2022. The results of operations for the interim periods presented are not necessarily indicative of the results to be expected for the full year.

Fiscal Year

We operate on a 52/53 week fiscal year, whereby the fiscal year ends on the last Saturday of December. Fiscal 2022 and 2021 contain 53 weeks and 52 weeks, respectively, and the nine months ended September 24, 2022 and September 25, 2021 each contained 39 weeks. Fiscal 2022 will end on December 31, 2022.

New Accounting Pronouncements

ASU 2021-08

In October 2021, the FASB issued ASU 2021-08, Business Combinations (Topic 805): Accounting for Contract Assets and Contract Liabilities from Contracts with Customers. The new guidance requires contract assets and contract liabilities acquired in a business combination to be recognized and measured by the acquirer on the acquisition date in accordance with Accounting Standards Codification 606, “Revenue from Contracts with Customers,” as if it had originated the contracts. The Company elected to early adopt on a prospective basis during the second quarter of fiscal 2022. The adoption did not have a material effect on the Company's Consolidated Financial Statements.

Fair Value

Whenever possible, the fair values of our financial assets and liabilities are determined using quoted market prices of identical securities or quoted market prices of similar securities from active markets. The three levels of inputs that may be used to measure fair value are as follows:

•Level 1 valuations are obtained from real-time quotes for transactions in active exchange markets involving identical securities;

•Level 2 valuations utilize significant observable inputs, such as quoted prices for similar assets or liabilities, quoted prices near the reporting date in markets that are less active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities; and

•Level 3 valuations utilize unobservable inputs to the valuation methodology and include our own data about assumptions market participants would use in pricing the asset or liability based on the best information available under the circumstances.

We did not have any transfers of assets or liabilities measured at fair value on a recurring basis to or from Level 1, Level 2 or Level 3 during the three and nine months ended September 24, 2022 or the year ended December 25, 2021.

The carrying values of Cash, Accounts receivable, net, Restricted cash, Prepaid expenses and other current assets, Accounts payable, and Accrued liabilities approximate fair value due to their short maturities.

No changes were made to our valuation techniques during the first nine months of fiscal 2022.

Assets and Liabilities Measured at Fair Value on a Non-Recurring BasisWe measure and report our non-financial assets such as Property, plant and equipment, Goodwill and Intangible assets at fair value on a non-recurring basis if we determine these assets to be impaired or in the period when we make a business acquisition.