Common Stock and Warrants - Summary of Warrants Accounts for as Liabilities (Detail) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Fair value of warrants at beginning of period	$ 1,205	$ 2,857
Issuance of warrants		3,016
Exercise of warrants		(1,200)
Change in fair value of warrants during the period	1,652	2,268
Fair value of warrants at end of period	$ 2,857	$ 6,941