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The cash outflow for cost incurred directly with the issuance of an equity security.

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Nature of the Business and Basis of Presentation - Additional Information (Details) $ / shares in Units, $ in Thousands				1 Months Ended		3 Months Ended		9 Months Ended
	Nov. 02, 2020 USD ($) $ / shares shares	Oct. 14, 2020 USD ($)	Mar. 28, 2020 USD ($)	Mar. 31, 2020 USD ($)	Oct. 31, 2017	Dec. 25, 2020 USD ($) continent location	Mar. 27, 2020 USD ($)	Dec. 25, 2020 USD ($) continent location	Dec. 27, 2019 USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Percentage of ownership interest sold					0.288
Number of locations \| location						16		16
Number of continents on which entity operates \| continent						4		4
Noncash or Part Noncash Divestitures [Line Items]
Noncash or part noncash divestiture, amount of consideration received								$ 0	$ 0
Equity investment in related party						$ 26,657	$ 0	26,657
Adjustments to additional paid in capital, capitalization changes						(527)		19,165
IPO
Noncash or Part Noncash Divestitures [Line Items]
Number of shares issued in transaction (in shares) \| shares	28,750,000
Offering price (in dollars per share) \| $ / shares	$ 14.00
Net proceeds	$ 321,425
Underwriting discounts	20,125
Estimated offering costs	$ 8,450
IPO - Selling Shareholders
Noncash or Part Noncash Divestitures [Line Items]
Number of shares issued in transaction (in shares) \| shares	3,750,000
COVID-19
Noncash or Part Noncash Divestitures [Line Items]
Proceeds from lines of credit				$ 43,000			$ 43,000
Estimated cash benefit, CARES Act, net operating losses						8,963		8,963
Estimated cash benefit, CARES Act, qualified improvement property						1,680		1,680
Estimated deferred payroll taxes, CARES Act						2,766		2,766
Estimated deferred payroll taxes, CARES Act, to be paid, third quarter of fiscal year 2022						1,383		1,383
Allegro Microsystems, Inc. \| IPO
Noncash or Part Noncash Divestitures [Line Items]
Number of shares issued in transaction (in shares) \| shares	25,000,000
Disposal Group, Disposed of by Sale, Not Discontinued Operations \| PSL
Noncash or Part Noncash Divestitures [Line Items]
Noncash or part noncash divestiture, amount of consideration received			$ 42,700
Noncash or part noncash divestiture, amount of consideration transferred			$ 15,000
Equity method investment, ownership percentage			30.00%
Equity investment in related party			$ 25,250
Income from equity method investments						949		1,407
Adjustments to additional paid in capital, capitalization changes								19,165
Adjustments to additional paid in capital, income tax benefit from noncash or part noncash divestiture								1,552
Disposal Group, Disposed of by Sale, Not Discontinued Operations \| PSL \| Sanken
Noncash or Part Noncash Divestitures [Line Items]
Ownership percentage by majority shareholder			70.00%
Disposal Group, Disposed of by Sale, Not Discontinued Operations \| PSL \| PSL
Noncash or Part Noncash Divestitures [Line Items]
Related party debt			$ 66,377
Repayments of related party notes receivable		$ 51,377
Note receivable from related party						51,377		51,377
Interest paid		762
Interest payable		$ 762				$ 762		$ 762