Fair Value Measurements - Additional Information (Detail) - CRG [Member] - Term Loan Agreement [Member] - USD ($)	1 Months Ended	6 Months Ended
	Mar. 31, 2019	Jun. 30, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Additional interest rate, event of default (as a percent)		4.00%
Debt instrument covenant compliance revenue targeted for fiscal year	$ 9,000,000
Derivative liability		$ 2,500,000	$ 2,100,000
Contingent Interest Beginning in 2020 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent payment of interest rate		4.00%
Contingent Interest Beginning in 2020 [Member] | Measurement Input, Discount Rate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated fair value of discount rate		70.00%
Contingent Interest Beginning in 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent payment of interest rate		4.00%
Contingent Interest Beginning in 2021 | Measurement Input, Discount Rate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated fair value of discount rate		30.00%