Stock based compensation - Summary the activity under the Company's stock option plan (Detail) $ / shares in Units, $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2020 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares
Share-based Payment Arrangement [Abstract]
Outstanding Number, Beginning balance | shares	1,073,044
Outstanding Number, Granted | shares	0
Outstanding Number, Forfeited | shares	0
Outstanding Number ,Exercised | shares	0
Outstanding Number , Ending balance | shares	1,073,044	1,073,044
Outstanding Number, Vested and expected to vest | shares	1,073,044
Outstanding Number, Exercisable | shares	426,980
Weighted Average Exercise price, Beginning balance | $ / shares	$ 2.45
Weighted Average Exercise price, Granted | $ / shares	0
Weighted Average Exercise price, Forfeited | $ / shares	0
Weighted Average Exercise price, Exercised | $ / shares	0
Weighted Average Exercise price, Ending balance | $ / shares	2.45	$ 2.45
Weighted Average Exercise price, Vested and expected to vest | $ / shares	2.45
Weighted Average Exercise price, Exercisable | $ / shares	$ 2.23
Weighted-Average Remaining Contractual Term	8 years 2 months 12 days	8 years 8 months 12 days
Weighted-Average Remaining Contractual Term, Vested and expected to vest	8 years 2 months 12 days
Weighted-Average Remaining Contractual Term, Exercisable	7 years 7 months 6 days
Aggregate Intrinsic Value | $	$ 906	$ 906
Aggregate Intrinsic Value, Vested and expected to vest | $	906	$ 906
Aggregate Intrinsic Value, Exercisable | $	$ 468