Components of Net Periodic Pension Cost Benefit (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1,051	$ 966	$ 1,060
Interest cost	4,912	4,986
Expected return on plan assets	(6,254)	(7,772)	(7,601)
Recognized actuarial loss	3,164	1,107	3,305
Net periodic cost	2,873	(714)	1,292
Components of net periodic cost (benefit)
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 4,912	$ 4,985	$ 4,528