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Equity - Common Stock - Additional Information (Detail) - shares | 6 Months Ended
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Jun. 30, 2021 | Jun. 30, 2020
Amarin Corporation Plc 2017 Employee Stock Purchase Plan | Ordinary Shares |  |
Stockholders Equity Note [Line Items] |  |
Issuance of common stock, net of transaction costs (shares) | 226,402 | 123,608

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