Leases - Additional Information (Detail) $ in Thousands		12 Months Ended
	Aug. 15, 2019 USD ($) RenewalOption	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Feb. 01, 2022 USD ($)
Lessee Lease Description [Line Items]
Incremental borrowing rate for purposes of calculation of lease liabilities		11.50%
Change in incremental borrowing rate		1.00%
Operating lease liability		$ 10,300	$ 10,600
Operating lease right-of-use asset		7,660	8,054
Operating lease expense		$ 2,200	$ 1,600	$ 1,500
Bridgewater
Lessee Lease Description [Line Items]
Lease commencement date	Aug. 15, 2019
Lease agreement term	11 years
Number of renewal options | RenewalOption	2
Lease renewal term	5 years
Description of lease agreement		Amarin will have a one-time option to terminate the agreement effective on the first day of the 97th month after the Commencement Date upon advance written notice and a termination payment specified in the Lease.
Lease termination description		one-time option to terminate the agreement effective on the first day of the 97th month after the Commencement Date
Lease termination existence of option to extend	true
Rent payment	$ 100
Zug | Subsequent Event
Lessee Lease Description [Line Items]
Lease agreement term					5 years
Rent payment					$ 200
Maximum
Lessee Lease Description [Line Items]
Short term lease period		12 months