Significant Accounting Policies - Additional Information (Detail) $ in Millions	3 Months Ended
Mar. 31, 2025 USD ($) Segment Customer	Mar. 31, 2024 USD ($)
Significant Accounting Policies [Line Items]
Trade receivables, credit period	45 days
Maturities period	24 months
Unrealized gain (loss) on held-to-maturity securities	$ 0.1
Segment Reporting, Expense Information Used by CODM, Description	Operating segments are defined as components of an enterprise about which separate financial information is available that is evaluated on a regular basis by the chief operating decision-maker, or CODM, in deciding how to allocate resources to an individual segment and in assessing performance of the segment. The Company currently operates in two business segments, U.S. and Europe, which are aggregated into a single reportable segment, for the development and commercialization of VASCEPA. A single management team that reports to the Company’s CODM, who is the Chief Executive Officer, comprehensively manages the business on an integrated basis for the purpose of allocating resources. The Company’s CODM does not currently assess segment performance or allocate resources based on a measure of total assets nor is it practical for the Company to disaggregate assets based on geography. Accordingly, a total asset measure has not been provided for segment disclosure. Accordingly, the Company does not have separately reportable segments.
Number of reportable segments \| Segment	1
Segment Reporting, CODM, Individual Title and Position or Group Name [Extensible Enumeration]	srt:ChiefExecutiveOfficerMember
Short Term Investments
Significant Accounting Policies [Line Items]
Maturities period	12 months
Long Term Investments
Significant Accounting Policies [Line Items]
Maturities period	12 months
Money Market Instruments
Significant Accounting Policies [Line Items]
Maturities period	90 days
Gross Product Sales \| Customer Concentration Risk
Significant Accounting Policies [Line Items]
Number of customers \| Customer	3
Customer A \| Gross Product Sales \| Customer Concentration Risk
Significant Accounting Policies [Line Items]
Concentration risk percentage	33.00%	28.00%
Customer A \| Accounts Receivable \| Customer Concentration Risk
Significant Accounting Policies [Line Items]
Concentration risk percentage	36.00%	37.00%
Customer B \| Gross Product Sales \| Customer Concentration Risk
Significant Accounting Policies [Line Items]
Concentration risk percentage	29.00%	35.00%
Customer B \| Accounts Receivable \| Customer Concentration Risk
Significant Accounting Policies [Line Items]
Concentration risk percentage	23.00%	31.00%
Customer C \| Gross Product Sales \| Customer Concentration Risk
Significant Accounting Policies [Line Items]
Concentration risk percentage	29.00%	29.00%
Customer C \| Accounts Receivable \| Customer Concentration Risk
Significant Accounting Policies [Line Items]
Concentration risk percentage	21.00%	22.00%
Internal Revenue Service (IRS)
Significant Accounting Policies [Line Items]
Open tax year	2018 2019
Maximum
Significant Accounting Policies [Line Items]
Unrealized gain (loss) on held-to-maturity securities		$ (0.1)

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Number of customers.

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Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

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Description of nature of expense information used by chief operating decision maker (CODM) to manage operation when segment expense information by category is not disclosed.

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