Restructuring - Schedule of Components of Liabilities (Detail)	3 Months Ended	9 Months Ended
	Sep. 30, 2019 USD ($)	Sep. 30, 2019 USD ($)
Restructuring Cost And Reserve [Line Items]
Restructuring expenses	$ 0	$ 1,492,000
Cash payments	(206,000)	(1,101,000)
Employee Severance And Other Benefits [Member] | Accrued Expenses and Other Current Liabilities [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring expenses		1,492,000
Cash payments		(1,101,000)
Liability included in accrued expenses and other current liabilities at September 30, 2019	$ 391,000	$ 391,000