Redeemable Convertible Preferred Stock - Schedule of Cumulative Dividends (Detail) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
Series A Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Preferred stock amount of cumulative dividend	$ 8,479	$ 7,482
Series B Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Preferred stock amount of cumulative dividend	10,014	$ 7,446
Series C Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Preferred stock amount of cumulative dividend	$ 392