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Related Party Transactions (Details) - USD ($) |  |  |  |  |  |  |  |  |  |  |  | 12 Months Ended
--- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | ---
Mar. 31, 2025 | Sep. 20, 2024 | Aug. 07, 2024 | Jul. 29, 2024 | Jul. 26, 2024 | Jul. 24, 2024 | Jul. 23, 2024 | Apr. 25, 2024 | Mar. 31, 2023 | Jul. 01, 2022 | Dec. 02, 2021 | Mar. 28, 2025 | Mar. 29, 2024 | Mar. 31, 2023
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net proceeds from issuance of common stock |  |  |  |  |  |  |  |  |  |  |  | $ 665,850,000 | $ 0 | $ 0
Recognized loss of fair value forward repurchase contract |  |  |  |  |  |  |  |  |  |  |  | 34,752,000 | 0 | 0
Net sales |  |  |  |  |  |  |  |  |  |  |  | 725,006,000 | 1,049,367,000 | 973,653,000
Trade accounts receivable, net |  |  |  |  |  |  |  |  |  |  |  | 84,598,000 | 118,508,000 |
Selling, general and administrative expenses |  |  |  |  |  |  |  |  |  |  |  | 161,680,000 | 188,429,000 | 191,922,000
Outstanding balance |  |  |  |  |  |  |  |  |  |  |  | 338,929,000 | 245,102,000 |
Interest income |  |  |  |  |  |  |  |  |  |  |  | 89,000 |  |
Periodic payment |  |  |  |  |  |  |  |  |  |  |  | $ 1,964,000 |  |
Share Repurchase Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Facilitation fee included in transaction expenses |  |  |  |  |  |  | $ 35,000,000 |  |  |  |  |  |  |
Facilitation fee |  |  |  | $ 35,000,000 |  |  |  |  |  |  |  |  |  |
Common Stock |  |  |  |  |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Issuance of common stock |  |  |  |  |  |  |  |  |  |  |  | 28,750,000 |  |
Common Stock | Share Repurchase Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Repurchase of common stock |  |  | 10,017,315 | 28,750,000 |  |  | 38,767,315 |  |  |  |  |  |  |
Repurchase of common stock aggregate consideration , value |  |  | $ 225,549,000 | $ 628,256,000 |  |  |  |  |  |  |  |  |  |
Common Stock | Equity Offering |  |  |  |  |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net proceeds from issuance of common stock |  |  |  |  | $ 665,850,000 |  |  |  |  |  |  |  |  |
Issuance of common stock |  |  |  |  | 28,750,000 | 25,000,000 |  |  |  |  |  |  |  |
Share price |  |  |  |  | $ 24 | $ 23.16 |  |  |  |  |  |  |  |
Underwriting discount |  |  |  |  | $ 24,150,000 |  |  |  |  |  |  |  |  |
Common Stock | Equity Offering | Minimum |  |  |  |  |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net proceeds from issuance of common stock |  |  |  |  |  |  | $ 300,000,000 |  |  |  |  |  |  |
Common Stock | Underwriters Option |  |  |  |  |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Issuance of common stock |  |  |  |  |  | 3,750,000 |  |  |  |  |  |  |  |
Polar Semiconductor, LLC |  |  |  |  |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss on extinguishment of debt |  | $ 2,804,000 |  |  |  |  |  |  |  |  |  |  |  |
Extinguishment of Debt, Amount |  | 10,350,000 |  |  |  |  |  |  |  |  |  |  |  |
Exchange for equity interests amounts of transaction |  |  |  |  |  |  |  | $ 175,000,000 |  |  |  |  |  |
Sanken |  |  |  |  |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Other accounts receivable from related party |  |  |  |  |  |  |  |  |  |  |  |  | 160,000 |
Sanken | Sanken Distribution Agreement, One-Time Sales Return |  |  |  |  |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net sales |  |  |  |  |  |  |  |  |  |  |  | $ 0 | 6,161,000 | 160,763,000
Trade accounts receivable, net |  |  |  |  |  |  |  |  |  |  |  | 0 | 0 |
Selling, general and administrative expenses |  |  |  |  |  |  |  |  | $ 5,000,000 |  |  |  |  |
Related party transaction amounts |  |  |  |  |  |  |  |  | $ 4,200,000 |  |  |  |  |
Distribution agreement period |  |  |  |  |  |  |  |  | 24 months |  |  |  |  |
PSL |  |  |  |  |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Purchases from related party |  |  |  |  |  |  |  |  |  |  |  | 55,001,000 | 60,426,000 | $ 58,056,000
Amounts due to related party |  |  |  |  |  |  |  |  |  |  |  | $ 6,535,000 | $ 1,621,000 |
PSL | Initial PSL Loan | Loans Payable |  |  |  |  |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Principal amount |  |  |  |  |  |  |  |  |  |  | $ 7,500,000 |  |  |
Interest rate |  |  |  |  |  |  |  |  |  |  | 1.26% |  |  |
Term |  |  |  |  |  |  |  |  |  |  | 4 years |  |  |
PSL | Secondary PSL Loan | Loans Payable |  |  |  |  |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Principal amount |  |  |  |  |  |  |  |  |  | $ 7,500,000 |  |  |  |
Interest rate |  |  |  |  |  |  |  |  |  | 2.99% |  |  |  |
Term |  |  |  |  |  |  |  |  |  | 4 years |  |  |  |
PSL | PSL Promissory Notes |  |  |  |  |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Extinguishment of Debt, Amount |  | $ 6,596,000 |  |  |  |  |  |  |  |  |  |  |  |
Sanken Electric Co., Ltd. |  |  |  |  |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Ownership percentage by majority shareholder |  |  |  |  |  |  |  |  |  |  |  | 32.40% |  |
Allegro Microsystems, Inc. | Polar Semiconductor, LLC |  |  |  |  |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Ownership percentage by majority shareholder |  |  |  |  |  |  |  | 10.20% |  |  |  |  |  |
Subsequent Event | Sanken | Sanken Distribution Agreement, One-Time Sales Return |  |  |  |  |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Distribution agreement period | 12 months |  |  |  |  |  |  |  |  |  |  |  |  |

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