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v3.20.1

Equity - Preferred Stock - Additional Information (Detail) |  | 1 Months Ended | 3 Months Ended |  |
--- | --- | --- | --- | --- | ---
Mar. 05, 2015 USD ($) shares | Apr. 30, 2020 shares | Mar. 31, 2020 £ / shares shares | Mar. 31, 2015 USD ($) | Dec. 31, 2019 £ / shares shares | Mar. 05, 2015 £ / shares shares | Mar. 05, 2015 $ / shares shares
Stockholders Equity Note [Line Items] |  |  |  |  |  |  |
Preferred stock, par value | £ / shares |  |  | £ 0.05 |  | £ 0.05 | £ 0.05 |
Private placement, closing date | Mar. 30, 2015 |  |  |  |  |  |
Aggregate gross proceeds | $ |  |  |  | $ 52,800,000 |  |  |
Estimated offering expense | $ |  |  |  | $ 700,000 |  |  |
Common stock, par value | £ / shares |  |  | £ 0.50 |  | £ 0.50 | £ 0.50 |
Number of shares issued for each preference shares |  |  |  |  |  | 0.1 | 0.1
Preferred stock, equivalent ordinary shares upon future consolidation outstanding |  |  | 28,931,746 |  | 28,931,746 |  |
Series A Preferred Stock |  |  |  |  |  |  |
Stockholders Equity Note [Line Items] |  |  |  |  |  |  |
American depositary shares conversion rate to preference shares |  |  | American Depositary Shares, each representing one (1) share of Amarin’s Series A Convertible Preference Shares |  |  |  |
Series A Preferred Stock | Subsequent Event |  |  |  |  |  |  |
Stockholders Equity Note [Line Items] |  |  |  |  |  |  |
Conversion of stock, shares converted |  | 237,713,680 |  |  |  |  |
Series A Preferred Stock | Minimum |  |  |  |  |  |  |
Stockholders Equity Note [Line Items] |  |  |  |  |  |  |
Beneficial ownership limitation | 4.99% |  |  |  |  |  |
Series A Preferred Stock | Maximum |  |  |  |  |  |  |
Stockholders Equity Note [Line Items] |  |  |  |  |  |  |
Beneficial ownership limitation | 19.90% |  |  |  |  |  |
Ordinary Shares |  |  |  |  |  |  |
Stockholders Equity Note [Line Items] |  |  |  |  |  |  |
Convertible senior notes, total ADS into which the debt is exchangeable |  |  | 6,283,333 |  |  |  |
Preferred stock, equivalent ordinary shares upon future consolidation outstanding |  |  | 28,931,746 |  |  |  |
Ordinary Shares | Subsequent Event |  |  |  |  |  |  |
Stockholders Equity Note [Line Items] |  |  |  |  |  |  |
Convertible senior notes, total ADS into which the debt is exchangeable |  | 23,771,368 |  |  |  |  |
Preferred stock, equivalent ordinary shares upon future consolidation outstanding |  | 5,160,378 |  |  |  |  |
American Depositary Shares | Series A Preferred Stock |  |  |  |  |  |  |
Stockholders Equity Note [Line Items] |  |  |  |  |  |  |
Issuance of stock (shares) | 352,150,790 |  |  |  |  |  |
Stock issued under private placement, value | $ | $ 52,800,000 |  |  |  |  |  |
Preferred Shares Basis |  |  |  |  |  |  |
Stockholders Equity Note [Line Items] |  |  |  |  |  |  |
Share conversion price | $ / shares |  |  |  |  |  |  | $ 0.15
Ordinary Shares Basis |  |  |  |  |  |  |
Stockholders Equity Note [Line Items] |  |  |  |  |  |  |
Share conversion price | $ / shares |  |  |  |  |  |  | $ 1.50

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