Summary of Significant Accounting Policies - Potentially Dilutive Securities Excluded from Calculation of Diluted Net (Loss) Income per Share Due to Anti-Dilutive Effect (Parenthetical) (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2019		Dec. 31, 2018		Dec. 31, 2017		Dec. 31, 2012
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Issued warrant to purchase common stock, amount	9,853,841		11,348,796		6,470,038
Warrants to Purchase Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Issued warrant to purchase common stock, amount	150,000	[1]	150,000	[1]	150,000	[1]	150,000
Warrant term							10 years
Issued warrant to purchase common stock, exercise price							$ 20.00

[1] In 2012, the Company issued a warrant with a ten-year term to purchase 150,000 shares of its common stock at an exercise price of $20.00 per share.