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Stock Based Compensation - Narrative (Detail) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock compensation expense (gain)	$ 2,700			$ 3,300			$ 7,500	$ 7,700
Unrecognized stock-based compensation cost	7,300						$ 7,300
Unrecognized share-based compensation expense, weighted-average recognition period (in years)							1 year 11 months 4 days
Common stock issuance ESPP Plan	808	$ 928	$ 796	$ 564	$ 653	$ 419
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized stock-based compensation cost	$ 4,200						$ 4,200
Unrecognized share-based compensation expense, weighted-average recognition period (in years)							1 year 10 months 24 days
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee stock purchase plan, discount rate (as a percent)							15.00%
Common stock issuance ESPP Plan (in shares)	29,853			28,672			105,241	101,959
Common stock issuance ESPP Plan	$ 200			$ 100			$ 600	$ 400