Nature of Business and Basis of Presentation - Additional Information (Detail)	1 Months Ended	3 Months Ended
	Sep. 30, 2018 Employee	Mar. 31, 2019 USD ($) Patient Employee Segment	Dec. 31, 2018 USD ($)
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]
REDUCE-IT study, number of patients enrolled and randomized | Patient		8,179
Number of operating segments | Segment		1
Total current assets		$ 355,319,000	$ 377,997,000
Cash and cash equivalents		211,089,000	249,227,000
Accounts receivable, net		79,485,000	66,523,000
Inventory		57,909,000	$ 57,802,000
Other debt outstanding		$ 0
Sales Representatives and Managers
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Number of sales professionals | Employee	170	440
Sales Representatives
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Number of sales professionals | Employee		400