Significant Accounting Policies - Additional Information (Detail) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2025 USD ($) Customer	Sep. 30, 2025 USD ($) Customer Segment	Sep. 30, 2024 USD ($)	Jun. 24, 2025 USD ($)
Significant Accounting Policies [Line Items]
Trade receivables, credit period		45 days
Maturities period		12 months
Number of reportable segments | Segment		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. Therefore, the Company does not have separate reportable segments.
Segment Reporting, CODM, Individual Title and Position or Group Name [Extensible Enumeration]		srt:ChiefExecutiveOfficerMember
Restructuring expenses	$ 9,406	$ 32,165
Global Restructuring Plan
Significant Accounting Policies [Line Items]
Restructuring expenses	$ 9,400	$ 32,200
Short 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	3
Customer A | Gross Product Sales | Customer Concentration Risk
Significant Accounting Policies [Line Items]
Concentration risk percentage		31.00%	29.00%
Customer A | Accounts Receivable | Customer Concentration Risk
Significant Accounting Policies [Line Items]
Concentration risk percentage		40.00%	41.00%
Customer B | Gross Product Sales | Customer Concentration Risk
Significant Accounting Policies [Line Items]
Concentration risk percentage		29.00%	34.00%
Customer B | Accounts Receivable | Customer Concentration Risk
Significant Accounting Policies [Line Items]
Concentration risk percentage		23.00%	30.00%
Customer C | Gross Product Sales | Customer Concentration Risk
Significant Accounting Policies [Line Items]
Concentration risk percentage		28.00%	28.00%
Customer C | Accounts Receivable | Customer Concentration Risk
Significant Accounting Policies [Line Items]
Concentration risk percentage		15.00%	17.00%
Minimum | Global Restructuring Plan
Significant Accounting Policies [Line Items]
Expected restructuring charges				$ 30,000
Minimum | Internal Revenue Service (IRS)
Significant Accounting Policies [Line Items]
Open tax year		2018
Maximum
Significant Accounting Policies [Line Items]
Unrealized gain (loss) on held-to-maturity securities	$ 100	$ 100	$ 300
Maximum | Global Restructuring Plan
Significant Accounting Policies [Line Items]
Expected restructuring charges				$ 37,000
Maximum | Internal Revenue Service (IRS)
Significant Accounting Policies [Line Items]
Open tax year		2019