Preferred and Common Stock Warrants - Schedule of Outstanding Warrants (Detail) - $ / shares	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018
Number of warrants
Number of warrants, Outstanding and exercisable warrants, Beginning Balance (in shares)	13,656,871	5,146,400	5,146,400
Conversion of warrant to purchase preferred shares to warrants for the purchase of common stock and adjusted for the Exchange Ratio and Reverse Stock split (in shares)		(4,657,350)
Number of warrants, Issuance of warrants for the purchase of common stock (in shares)	0	5,000
Number of warrants, Exercised (in shares)	0	0
Number of warrants, Cancelled (in shares)	0	0
Number of warrants, Outstanding and exercisable warrants, Ending Balance (in shares)	13,656,871	494,050	13,656,871	5,146,400
Weighted Average Exercise Price
Weighted Average Exercise Price, Outstanding and exercisable warrants, Beginning Balance (in usd per share)	$ 13.68	$ 1.94	$ 1.94
Conversion of warrant to purchase preferred shares to warrants for the purchase of common stock and adjusted for the Exchange Ratio and Reverse Stock Split (in usd per share)		1.94
Weighted Average Exercise Price, Issuance of warrants for the purchase of common stock (in usd per share)		19.80
Weighted Average Exercise Price, Exercised (in usd per share)		0
Weighted Average Exercise Price, Cancelled (in usd per share)		0
Weighted Average Exercise Price, Outstanding and exercisable warrants, Ending Balance (in usd per share)	$ 13.68	$ 20.39	$ 13.68	$ 1.94
Weighted Average Contractual Term (Years)	4 years 4 months 2 days	3 years 14 days	4 years 7 months 2 days	4 years 2 months 23 days