Stockholders' Equity - Stock Options and Employee Stock Purchase Plan - Additional Information (Detail) - USD ($)			12 Months Ended
	Aug. 14, 2018	Apr. 24, 2017	Mar. 31, 2020		Mar. 31, 2019
Class Of Stock [Line Items]
Issuances of common stock from stock option exercises, Shares			0		622,192
Weighted-average remaining contractual term of stock options exercisable			7 years 4 months 2 days
Weighted-average remaining contractual term of stock options outstanding			7 years 4 months 2 days
Number of common stock shares approved under ESPP			27,418,631
Expected life of options			6 years		6 years
2012 Plan [Member]
Class Of Stock [Line Items]
Issuances of common stock from stock option exercises, Shares			342,500
Inducement Award Agreement [Member]
Class Of Stock [Line Items]
Vesting period		4 years
Award vesting conditions			These stock options vest over a four-year period, with a quarter of the option shares vesting on the one-year anniversary of the vesting commencement date and the remaining options shares vesting in equal quarterly installments over the next 12 quarterly periods.
Award vesting percentage			25.00%
Inducement Award Agreement [Member] | CEO [Member]
Class Of Stock [Line Items]
Stock options granted		2,088,212
Inducement Award Agreement [Member] | CMO [Member]
Class Of Stock [Line Items]
Stock options granted	974,694
2016 Employee Stock Purchase Plan [Member]
Class Of Stock [Line Items]
Number of common stock shares approved under ESPP			1,500,000
Employee subscription rate			15.00%
Compensation amount per employee			$ 25,000
Number of shares per employee			10,000
Fair market value at discount			85.00%
Purchase period			6 months
Initial offering period			2016-09
Description of plan			Shares under the ESPP are purchased at 85 percent of the fair market value at the lower of (i) the closing price on the first trading day of the six-month purchase period or (ii) the closing price on the last trading day of the six-month purchase period.
Expected life of options			6 months	[1]	6 months
Shares issued under ESPP			0
Shares remaining available for purchase under ESPP			1,188,718

[1] There were no participants in the ESPP for the purchase period September 1, 2019 – February 29, 2020 nor any participants in the ESPP for the current purchase period (beginning March 1, 2020).