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Liability Related to Sale of Future Royalties - Additional Information (Detail) - USD ($) $ in Thousands |  | 3 Months Ended | 70 Months Ended
--- | --- | --- | ---
Feb. 24, 2012 | Mar. 31, 2020 | Dec. 31, 2019 | Mar. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2017
Liability Related to Sale of Future Royalties [Line Items] |  |  |  |  |  |  |
Non-cash royalty revenue related to sale of future royalties |  | $ 9,895 |  | $ 8,230 |  |  |
Non-cash interest expense on liability related to sale of future royalties |  | $ (6,968) |  | $ (6,065) |  |  |
Annual interest rate |  |  | 19.50% |  | 18.70% | 17.60% | 17.00%
Prospective interest rate |  |  | 38.00% |  | 29.00% | 21.00% |
Purchase and Sale Agreement with RPI |  |  |  |  |  |  |
Liability Related to Sale of Future Royalties [Line Items] |  |  |  |  |  |  |
Proceeds from sale of royalty rights | $ 124,000 |  |  |  |  |  |
Transaction costs related to sale of potential future royalties | $ 4,400 |  |  |  |  |  |

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- Definition Amount, before accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28555-108399 + Details
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