Stockholders' Equity - Assumptions Used to Calculate Fair Value of Warrants (Detail) - Letter Agreement Warrants [Member]	Dec. 23, 2019 yr	Sep. 26, 2019 yr	Dec. 11, 2018 yr	Jul. 30, 2018 yr	Dec. 05, 2017 yr
Expected Volatility [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Measurement input	110.41	110.35	104.46	95.29	90.00
Expected Life of Option, in Years [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Measurement input	7.0	7.0	7.0	7.0	7.0
Risk-Free Interest Rate [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Measurement input	1.84	1.65	2.77	2.94	2.80
Expected Dividend Yield [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Measurement input	0.00	0.00	0.00	0.00	0.00