| Pay vs Performance Disclosure - USD ($) | 12 Months Ended |
| Dec. 31, 2022 | Dec. 31, 2021 | Dec. 31, 2020 |
| Pay vs Performance Disclosure [Table] | | | |
| Pay vs Performance [Table Text Block] | Value of Initial Fixed $100 Investment based on: (3) Year Summary Compensation Table Total for PEO (1) ($) Compensation Actually Paid to PEO (1)(2) ($) Average Summary Compensation Table Total for Non-PEO NEOs (1) ($) Average Compensation Actually Paid to Non-PEO NEOs (1)(2) ($) Total Stockholder Return Peer Group Total Stockholder Return Net Income 2022 4,806,435 967,855 1,470,480 535,641 37.51 113.65 (192) 2021 4,735,817 (1,607,944) 1,270,411 (724,313) 89.61 126.45 (178) 2020 3,835,030 9,627,615 1,695,086 2,856,434 186.44 126.42 (121) | | |
| Named Executive Officers, Footnote [Text Block] | Alexander D. Macrae was our PEO for each year presented. The individuals comprising the Non-PEO NEOs for each year presented are listed below. 2020 2021 2022 D. Mark McClung Prathyusha Duraibabu Prathyusha Duraibabu R. Andrew Ramelmeier D. Mark McClung D. Mark McClung Sung H. Lee R. Andrew Ramelmeier R. Andrew Ramelmeier Gary H. Loeb Robert J. Schott Jason D. Fontenot Stéphane Boissel Sung H. Lee | | |
| Peer Group Issuers, Footnote [Text Block] | The peer group total stockholder return, or TSR, set forth in this table utilizes the NASDAQ Biotechnology Index, which we also utilize in the stock performance graph required by Item 201(e) of Regulation S-K included in our Annual Report for the year ended December 31, 2022. The comparison assumes $100 was invested for the period starting December 31, 2019, through the end of the listed year in the Company and in the NASDAQ Biotechnology Index, respectively. Historical stock performance is not necessarily indicative of future stock performance. | | |
| PEO Total Compensation Amount | $ 4,806,435 | $ 4,735,817 | $ 3,835,030 |
| PEO Actually Paid Compensation Amount | $ 967,855 | (1,607,944) | 9,627,615 |
| Adjustment To PEO Compensation, Footnote [Text Block] | Compensation actually paid reflects the exclusions and inclusions of certain amounts for the PEO and the Non-PEO NEOs as set forth below. Equity values are calculated in accordance with FASB ASC Topic 718. Amounts in the “Exclusion of Stock Awards and Option Awards” column are the totals from the “Stock Awards and Option Awards” columns set forth in the Summary Compensation Table. Year Summary Compensation Table Total for PEO Exclusion of Stock Awards and Option Awards for PEO Inclusion of Equity Values for PEO Compensation Actually Paid to PEO 2022 4,806,435 (3,635,081) (203,499) 967,855 2021 4,735,817 (3,595,425) (2,748,336) (1,607,944) 2020 3,835,030 (2,636,246) 8,428,831 9,627,615 Year Average Summary Compensation Table Total for Non-PEO NEOs Average Exclusion of Stock Awards and Option Awards for Non-PEO NEOs Average Inclusion of Equity Values for Non-PEO NEOs Average Compensation Actually Paid to Non-PEO NEOs 2022 1,470,480 (809,374) (125,465) 535,641 2021 1,270,411 (782,085) (1,212,639) (724,313) 2020 1,695,086 (1,077,218) 2,238,566 2,856,434 The amounts in the “Inclusion of Equity Values” columns in the tables above are derived from the amounts set forth in the following tables: Year Year-End Fair Value of Equity Awards Granted During Year That Remained Unvested as of Last Day of Year for PEO Change in Fair Value from Last Day of Prior Year to Last Day of Year of Unvested Equity Awards for PEO Vesting-Date Fair Value of Equity Awards Granted During Year that Vested During Year for PEO Change in Fair Value from Last Day of Prior Year to Vesting Date of Unvested Equity Awards that Vested During Year for PEO Fair Value at Last Day of Prior Year of Equity Awards Forfeited During Year for PEO Total - Inclusion of Equity Values for PEO 2022 1,859,626 (1,370,919) — (692,206) — (203,499) 2021 2,278,773 (3,269,075) — (1,758,034) — (2,748,336) 2020 6,598,645 1,787,376 — 42,810 — 8,428,831 Year Average Year-End Fair Value of Equity Awards Granted During Year That Remained Unvested as of Last Day of Year for Non-PEO NEOs ($) Average Change in Fair Value from Last Day of Prior Year to Last Day of Year of Unvested Equity Awards for Non-PEO NEOs Average Vesting-Date Fair Value of Equity Awards Granted During Year that Vested During Year for Non-PEO NEOs Average Change in Fair Value from Last Day of Prior Year to Vesting Date of Unvested Equity Awards that Vested During Year for Non-PEO NEOs Average Fair Value at Last Day of Prior Year of Equity Awards Forfeited During Year for Non-PEO NEOs Total - Average Inclusion of Equity Values for Non-PEO NEOs 2022 414,159 (358,894) — (180,730) — (125,465) 2021 464,998 (555,131) — (245,081) (877,425) (1,212,639) 2020 1,973,256 500,063 — 19,774 (254,527) 2,238,566 | | |
| Non-PEO NEO Average Total Compensation Amount | $ 1,470,480 | 1,270,411 | 1,695,086 |
| Non-PEO NEO Average Compensation Actually Paid Amount | $ 535,641 | (724,313) | 2,856,434 |
| Adjustment to Non-PEO NEO Compensation Footnote [Text Block] | Compensation actually paid reflects the exclusions and inclusions of certain amounts for the PEO and the Non-PEO NEOs as set forth below. Equity values are calculated in accordance with FASB ASC Topic 718. Amounts in the “Exclusion of Stock Awards and Option Awards” column are the totals from the “Stock Awards and Option Awards” columns set forth in the Summary Compensation Table. Year Summary Compensation Table Total for PEO Exclusion of Stock Awards and Option Awards for PEO Inclusion of Equity Values for PEO Compensation Actually Paid to PEO 2022 4,806,435 (3,635,081) (203,499) 967,855 2021 4,735,817 (3,595,425) (2,748,336) (1,607,944) 2020 3,835,030 (2,636,246) 8,428,831 9,627,615 Year Average Summary Compensation Table Total for Non-PEO NEOs Average Exclusion of Stock Awards and Option Awards for Non-PEO NEOs Average Inclusion of Equity Values for Non-PEO NEOs Average Compensation Actually Paid to Non-PEO NEOs 2022 1,470,480 (809,374) (125,465) 535,641 2021 1,270,411 (782,085) (1,212,639) (724,313) 2020 1,695,086 (1,077,218) 2,238,566 2,856,434 The amounts in the “Inclusion of Equity Values” columns in the tables above are derived from the amounts set forth in the following tables: Year Year-End Fair Value of Equity Awards Granted During Year That Remained Unvested as of Last Day of Year for PEO Change in Fair Value from Last Day of Prior Year to Last Day of Year of Unvested Equity Awards for PEO Vesting-Date Fair Value of Equity Awards Granted During Year that Vested During Year for PEO Change in Fair Value from Last Day of Prior Year to Vesting Date of Unvested Equity Awards that Vested During Year for PEO Fair Value at Last Day of Prior Year of Equity Awards Forfeited During Year for PEO Total - Inclusion of Equity Values for PEO 2022 1,859,626 (1,370,919) — (692,206) — (203,499) 2021 2,278,773 (3,269,075) — (1,758,034) — (2,748,336) 2020 6,598,645 1,787,376 — 42,810 — 8,428,831 Year Average Year-End Fair Value of Equity Awards Granted During Year That Remained Unvested as of Last Day of Year for Non-PEO NEOs ($) Average Change in Fair Value from Last Day of Prior Year to Last Day of Year of Unvested Equity Awards for Non-PEO NEOs Average Vesting-Date Fair Value of Equity Awards Granted During Year that Vested During Year for Non-PEO NEOs Average Change in Fair Value from Last Day of Prior Year to Vesting Date of Unvested Equity Awards that Vested During Year for Non-PEO NEOs Average Fair Value at Last Day of Prior Year of Equity Awards Forfeited During Year for Non-PEO NEOs Total - Average Inclusion of Equity Values for Non-PEO NEOs 2022 414,159 (358,894) — (180,730) — (125,465) 2021 464,998 (555,131) — (245,081) (877,425) (1,212,639) 2020 1,973,256 500,063 — 19,774 (254,527) 2,238,566 | | |
| Compensation Actually Paid vs. Total Shareholder Return [Text Block] | As required by Item 402(v) of Regulation S-K, we are providing the following graphs to illustrate the relationship between the pay and performance figures that are included in the pay versus performance tabular disclosure above. In addition, the first graph below further illustrates the relationship between our TSR and that of the NASDAQ Biotechnology Index. As noted above, “compensation actually paid” for purposes of the tabular disclosure and the following graphs were calculated in accordance with SEC rules and do not fully represent the actual final amount of compensation earned by or actually paid to our NEOs during the applicable year. | | |
| Compensation Actually Paid vs. Net Income [Text Block] | | | |
| Total Shareholder Return Amount | $ 37.51 | 89.61 | 186.44 |
| Peer Group Total Shareholder Return Amount | 113.65 | 126.45 | 126.42 |
| Net Income (Loss) | $ (192,000,000) | (178,000,000) | (121,000,000) |
| PEO Name | Alexander D. Macrae | | |
| PEO [Member] | Stock Awards And Option Awards Reported Value [Member] | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | $ (3,635,081) | (3,595,425) | (2,636,246) |
| PEO [Member] | Equity Awards Adjustments [Member] | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | (203,499) | (2,748,336) | 8,428,831 |
| PEO [Member] | Equity Awards Granted During The Year, Unvested [Member] | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount, Equity Awards | 1,859,626 | 2,278,773 | 6,598,645 |
| PEO [Member] | Equity Awards Granted In Prior Years, Unvested [Member] | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount, Equity Awards | (1,370,919) | (3,269,075) | 1,787,376 |
| PEO [Member] | Equity Awards Granted During The Year, Vested [Member] | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount, Equity Awards | 0 | 0 | 0 |
| PEO [Member] | Equity Awards Granted In Prior Years, Vested [Member] | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount, Equity Awards | (692,206) | (1,758,034) | 42,810 |
| PEO [Member] | Equity Awards Forfeited During The Year [Member] | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount, Equity Awards | 0 | 0 | 0 |
| Non-PEO NEO [Member] | Stock Awards And Option Awards Reported Value [Member] | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | (809,374) | (782,085) | (1,077,218) |
| Non-PEO NEO [Member] | Equity Awards Adjustments [Member] | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | (125,465) | (1,212,639) | 2,238,566 |
| Non-PEO NEO [Member] | Equity Awards Granted During The Year, Unvested [Member] | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount, Equity Awards | 414,159 | 464,998 | 1,973,256 |
| Non-PEO NEO [Member] | Equity Awards Granted In Prior Years, Unvested [Member] | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount, Equity Awards | (358,894) | (555,131) | 500,063 |
| Non-PEO NEO [Member] | Equity Awards Granted During The Year, Vested [Member] | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount, Equity Awards | 0 | 0 | 0 |
| Non-PEO NEO [Member] | Equity Awards Granted In Prior Years, Vested [Member] | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount, Equity Awards | (180,730) | (245,081) | 19,774 |
| Non-PEO NEO [Member] | Equity Awards Forfeited During The Year [Member] | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount, Equity Awards | $ 0 | $ (877,425) | $ (254,527) |
