Stockholders' Equity (Detail) - shares |
Mar. 31, 2019 |
Dec. 31, 2018 |
---|---|---|
Common Stock, Capital Shares Reserved for Future Issuance | 33,371,464 | 33,432,421 |
Warrant [Member] | ||
Common Stock, Capital Shares Reserved for Future Issuance | 17,678,074 | 17,732,700 |
2003 Stock Incentive Plan | ||
Common Stock, Capital Shares Reserved for Future Issuance | 6,584,397 | 6,590,725 |
2018 Equity Incentive Plan | ||
Common Stock, Capital Shares Reserved for Future Issuance | 9,108,996 | 9,108,996 |