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Nature of Business and Basis of Presentation - Additional Information (Detail) $ in Thousands |  |  | 1 Months Ended | 9 Months Ended |  |  |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | --- | ---
Jan. 31, 2017 | Jan. 20, 2017 USD ($) | Jan. 31, 2012 USD ($) | Sep. 30, 2017 USD ($) Patient Employee Segment | Dec. 31, 2016 USD ($) | Sep. 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] |  |  |  |  |  |  |  |  |
REDUCE-IT study, number of patients enrolled and randomized | Patient |  |  |  | 8,175 |  |  |  |  |
Number of sales professionals | Employee |  |  |  | 150 |  |  |  |  |
Number of operating segments | Segment |  |  |  | 1 |  |  |  |  |
Cash and cash equivalents |  |  |  | $ 79,086 | $ 98,251 | $ 117,562 | $ 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% |  |  |  |  |  |

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