Equity - Narrative (Detail) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended		3 Months Ended						9 Months Ended
	Jun. 30, 2019	May 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock compensation expense (gain)			$ 3,300			$ 1,100			$ 7,700	$ 5,000
Unrecognized stock-based compensation cost			5,700						$ 5,700
Unrecognized share-based compensation expense, weighted-average recognition period (in years)									1 year 4 months 13 days
Common stock issuance ESPP Plan			$ 564	$ 653	$ 419	$ 267	$ 231	$ 267
Working capital adjustment, return of shares (in shares)	99,254
Issuance of common stock, net									$ 10,132	$ 6,535
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)			28,672			21,100			101,959	87,288
Common stock issuance ESPP Plan			$ 100			$ 100			$ 400	$ 200
Public Stock Offering
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares issued in offering		8,050,000
Sale of stock (in dollars per share)		$ 21.25
Issuance of common stock, net		$ 171,100
Consideration received from offering		160,800
Payments of stock issuance costs		$ 10,300