Nature of Business and Basis of Presentation - Additional Information (Detail)	1 Months Ended	9 Months Ended
	Sep. 30, 2018 Employee	Sep. 30, 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 sales professionals | Employee		400
Number of operating segments | Segment		1
Total current assets		$ 848,110,000	$ 377,997,000
Cash and cash equivalents		673,207,000	249,227,000
Accounts receivable, net		103,583,000	66,523,000
Inventory		54,557,000	$ 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
Direct Sales Force
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Number of sales professionals | Employee		800