Marketable Securities and Fair Value - Additional Information (Detail) - USD ($) |
12 Months Ended | ||||
|---|---|---|---|---|---|
Dec. 31, 2017 |
Dec. 31, 2016 |
Aug. 01, 2017 |
Dec. 31, 2015 |
Dec. 31, 2014 |
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| Investments Debt And Equity Securities [Abstract] | |||||
| Shares of common stock to be purchased with warrants | 377,273 | 17,310 | 377,273 | 17,310 | 14,254 |
| Realized gain or losses | $ 0 | $ 0 | |||
| Long-term debt, carrying value | $ 3,500,000 | $ 5,600,000 | |||
| X | ||||||||||
- Definition This item represents the difference between the gross realized gains and losses realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities. Additionally, this item would include any losses recognized for other than temporary impairments (OTTI) of the subject investments in debt and equity securities. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
- Definition Number of warrants or rights outstanding. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
- References No definition available.
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| X | ||||||||||
- Definition Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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