Restructuring Activities - Summary of Charges Related to Restructuring Activities (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Restructuring Cost And Reserve [Line Items]
Accrued Restructuring Expenses			$ 66,000	$ 921,000
Expenses	$ 0		0	4,825,000
Less: Payments and Adjustments			(59,000)
Less: Payments		$ (800,000)		(5,624,000)
Accrued Restructuring Expenses	7,000	122,000	7,000	122,000
Severance Benefits and Related Costs Due to Workforce Reduction [Member]
Restructuring Cost And Reserve [Line Items]
Accrued Restructuring Expenses			66,000	921,000
Expenses				4,825,000
Less: Payments and Adjustments			(59,000)
Less: Payments				(5,624,000)
Accrued Restructuring Expenses	$ 7,000	$ 122,000	$ 7,000	$ 122,000