Components of Net Periodic Benefit Cost (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan [Abstract]
Service cost	$ 50	$ 38	$ 66
Interest cost	62	46	91
Expected return on plan assets	(18)	(11)	(10)
Amortization of prior service cost	69	69	65
Amortization of net transition obligation	0	22	0
Amortization of plan loss	20	0	0
Recognized actuarial net loss	0	0	17
Net periodic pension benefit cost	$ 183	$ 164	$ 229