Income Taxes - Additional Information (Detail) - USD ($)		12 Months Ended
	Mar. 27, 2020	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Income Taxes [Line Items]
Total amount of unrecognized tax benefits that would affect the tax rate if recognized		$ 8,200,000	$ 7,900,000
Interest related to uncertain tax positions		500,000	900,000
Penalties related to uncertain tax positions		0	0
Gross liabilities to expire in 2023		0
Provision for income taxes		(1,998,000)	(3,562,000)	$ (745,000)
Decrease in net operating loss carryforwards from prior years		15,600,000
Tax credit carryforwards		2,639,000	15,803,000
Undistributed earning retained indefinitely for reinvestment by foreign subsidiary		0
Unrecognized deferred income tax liability		0
ASU No. 2016-09
Income Taxes [Line Items]
Provisions benefit for income taxes		600,000	100,000	3,700,000
CARES Act
Income Taxes [Line Items]
Carry back net operating losses arising beginning year	2018
Carry back net operating losses arising end year	2020
Net operating loss carryback period	5 years
Provision for income taxes		$ 0	$ 0	$ 2,500,000
Ireland
Income Taxes [Line Items]
Corporate tax rate		25.00%	25.00%	25.00%
Ireland | Amarin Pharmaceuticals Ireland Limited
Income Taxes [Line Items]
Corporate tax rate		12.50%	12.50%	12.50%
Ireland | Non-Trading Activity
Income Taxes [Line Items]
Corporate tax rate		25.00%
Ireland | Trading Activity
Income Taxes [Line Items]
Corporate tax rate		12.50%
U.S. and Non-U.S.
Income Taxes [Line Items]
Foreign net operating loss carryforwards		$ 834,400,000
U.S. Federal
Income Taxes [Line Items]
Tax credit carryforwards		$ 9,500,000
U.S. Federal | Minimum
Income Taxes [Line Items]
Tax credit carryforward expiration year		2023
U.S. Federal | Maximum
Income Taxes [Line Items]
Tax credit carryforward expiration year		2042
State
Income Taxes [Line Items]
Tax credit carryforwards		$ 3,700,000
State | Minimum
Income Taxes [Line Items]
Tax credit carryforward expiration year		2023
State | Maximum
Income Taxes [Line Items]
Tax credit carryforward expiration year		2042