Nature of Business and Basis of Presentation - Additional Information (Detail) $ in Thousands			1 Months Ended	6 Months Ended
	Jan. 31, 2017	Jan. 20, 2017 USD ($)	Jan. 31, 2012 USD ($)	Jun. 30, 2017 USD ($) Employee Segment Patient	Dec. 31, 2016 USD ($)	Jun. 30, 2016 USD ($)	Dec. 31, 2015 USD ($)	Nov. 30, 2015 USD ($)	May 31, 2014 USD ($)
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Number of sales professionals | Employee				150
Number of operating segments | Segment				1
REDUCE-IT study, number of patients enrolled and randomized | Patient				8,175
Cash and cash equivalents				$ 85,464	$ 98,251	$ 72,491	$ 106,961
Convertible Debt
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Convertible senior notes, stated interest rate				3.50%
Convertible Debt | 2017 Notes
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Convertible senior notes, principal amount		$ 30,000		$ 30,000
Convertible senior notes, due date		2047
Convertible senior notes, stated interest rate		3.50%
Convertible senior notes, repurchase price at option of the issuer		100.00%
Convertible Debt | 2012 Notes
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Convertible senior notes, principal amount			$ 150,000	$ 0	$ 15,100			$ 15,100	$ 31,300
Convertible senior notes, due date	2032		2032
Convertible senior notes, stated interest rate	3.50%		3.50%
Convertible senior notes, repurchase price at option of the issuer	100.00%		100.00%