Investments and Fair Value Instruments - Summary of Warrant Liabilities Measured and Recorded on Recurring Basis using Black-Scholes Model (Detail) - Common Stock Warrant Liability [Member] - Level 3 [Member]	Dec. 31, 2021	Dec. 31, 2020
Expected Term [Member] | January 2021 Offering [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Expected term (in years)	4 years 6 months 29 days
Expected Term [Member] | September 2019 Offering [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Expected term (in years)	3 years 2 months 12 days	4 years 2 months 12 days
Expected Term [Member] | June 2019 Offering [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Expected term (in years)	2 years 11 months 15 days	3 years 11 months 15 days
Expected Term [Member] | March 2018 Offering [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Expected term (in years)	1 year 2 months 19 days	2 years 2 months 19 days
Expected Volatility [Member] | January 2021 Offering [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Warrants and rights outstanding, measurement input	129.8
Expected Volatility [Member] | September 2019 Offering [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Warrants and rights outstanding, measurement input	109.7	135.0
Expected Volatility [Member] | June 2019 Offering [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Warrants and rights outstanding, measurement input	110.8	135.0
Expected Volatility [Member] | March 2018 Offering [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Warrants and rights outstanding, measurement input	86.0	130.0
Risk-Free Interest Rate [Member] | January 2021 Offering [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Warrants and rights outstanding, measurement input	1.2
Risk-Free Interest Rate [Member] | September 2019 Offering [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Warrants and rights outstanding, measurement input	0.9	0.3
Risk-Free Interest Rate [Member] | June 2019 Offering [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Warrants and rights outstanding, measurement input	0.8	0.3
Risk-Free Interest Rate [Member] | March 2018 Offering [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Warrants and rights outstanding, measurement input	0.5	0.1
Expected Dividend Yield [Member] | January 2021 Offering [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Warrants and rights outstanding, measurement input	0
Expected Dividend Yield [Member] | September 2019 Offering [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Warrants and rights outstanding, measurement input	0	0
Expected Dividend Yield [Member] | June 2019 Offering [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Warrants and rights outstanding, measurement input	0	0
Expected Dividend Yield [Member] | March 2018 Offering [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Warrants and rights outstanding, measurement input	0	0