Share-Based Payment Awards - Employee Stock Purchase Plan - Additional Information (Detail) - USD ($)		3 Months Ended	9 Months Ended
	Jun. 25, 2019	Sep. 30, 2020	Sep. 30, 2020	Dec. 31, 2019
Class of Stock [Line Items]
Employee stock purchase plan aggregate fair market value of common stock		$ 107,000	$ 294,000
Common stock, shares issued		131,421,846	131,421,846	109,417,322
Employee Stock Purchase Plan [Member]
Class of Stock [Line Items]
Shares of common stock reserved for issuance	1,100,000
Price of common stock purchased twice a year under ESPP, percent	85.00%
Employee stock purchase plan aggregate fair market value of common stock	$ 25,000
Employee stock purchase plan aggregate fair market value of common stock shares	50,000
Offering period, start date	Aug. 01, 2019
Offering period, end date	Jan. 31, 2020
Common stock, shares issued		336,975	336,975