Equity - Common Stock - Additional Information (Detail) - shares	6 Months Ended
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

Number of new stock issued during the period.

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Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration