Note 8 - Liability Related to Sale of Future Royalties - Activity of Liability Related to Sale of Future Royalties (Details) - USD ($) $ in Thousands |
1 Months Ended | 12 Months Ended | 27 Months Ended | ||
|---|---|---|---|---|---|
Sep. 30, 2015 |
Dec. 31, 2017 |
Dec. 31, 2016 |
Dec. 31, 2015 |
Dec. 31, 2017 |
|
| Liability related to sale of future royalties — beginning balance | $ 72,987 | ||||
| Proceeds from sale of future royalties | $ 61,200 | $ 61,184 | 61,184 | ||
| Non-cash royalty revenue | (120) | (127) | |||
| Non-cash interest expense recognized | 10,721 | 9,382 | $ 2,428 | 22,531 | |
| Liability related to sale of future royalties as of December 31, 2017 | 83,588 | 72,987 | 83,588 | ||
| Less: current portion | (604) | (764) | (604) | ||
| Liability related to sale of future royalties — net of current portion | $ 82,984 | $ 72,223 | $ 82,984 | ||