Net Periodic Benefit Cost for Plan (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1,729	$ 1,081
Interest cost	134	163
Expected return on plan assets	(96)	(137)
Amortization of prior service cost	329	150
Net periodic benefit cost	$ 2,096	$ 1,257