Leases - Schedule of components of lease expense (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2019 USD ($)
Leases [Abstract]
Operating lease cost	$ 913	[1]
Finance lease cost:
Amortization of right-of-use assets	77
Interest on lease liability	92
Total finance lease cost	169
Total lease cost	$ 1,082

[1] includes variable lease costs which are immaterial