Leases - Schedule of components of lease expense (Detail) - USD ($) $ in Thousands		3 Months Ended	6 Months Ended
		Jun. 30, 2019	Jun. 30, 2019
Leases [Abstract]
Operating lease cost	[1]	$ 926	$ 1,839
Finance lease cost:
Amortization of right-of-use assets		77	154
Interest on lease liability		91	183
Total finance lease cost		168	337
Total lease cost		$ 1,094	$ 2,176

[1] includes variable lease costs which are immaterial