Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 01, 2019
Summary Of Significant Accounting Policies [Line Items]
Accumulated deficit	$ 220,988				$ 126,402				$ 220,988	$ 126,402
Net loss	$ 27,704	$ 27,548	$ 21,172	$ 18,009	$ 17,338	$ 18,588	$ 15,473	$ 13,376	94,433	64,775	$ 41,377
Net cash used in operating activities									85,011	38,162	34,971
Impairment losses									$ 0	$ 0	0
Lessor financed improvement incentives due but not yet received											$ 1,200
Percentage of realized upon ultimate settlement									50.00%
Accounting Standards Update 2016-02 [Member]
Summary Of Significant Accounting Policies [Line Items]
Accumulated deficit												$ 126,555
Derecognized property, plant, and equipment												15,400
Derecognized property, plant, and equipment accumulated depreciation												900
Derecognized of financing lease obligation												$ 10,500