Quarterly report pursuant to Section 13 or 15(d)

Marketable Securities - Additional Information (Detail)

v3.10.0.1
Marketable Securities - Additional Information (Detail)
9 Months Ended 12 Months Ended
Sep. 30, 2018
USD ($)
Security
Dec. 31, 2017
USD ($)
Security
Marketable Securities [Abstract]    
Maturity period classified current investments Less than one year Less than one year
Number of securities in unrealized loss position for less than one year | Security 26 32
Aggregate fair value of debt securities | $ $ 24,066,817 $ 39,858,864