Debt - Summary of Future Minimum Principal and Interest Payments (Detail) - USD ($) $ in Thousands		Jun. 30, 2019	Dec. 31, 2018
Debt Disclosure [Abstract]
2021		$ 2,100
2022		2,800
2023		10,100
Total future payments		15,000	$ 12,500
2019	[1]	936
2020	[1]	1,872
2021	[1]	1,654
2022	[1]	1,304
2023	[1]	955
Total future payments	[1]	$ 6,721

[1] estimated using LIBOR rates as at June 30, 2019