Components of Net Periodic Pension Cost Benefit (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 926	$ 1,051	$ 966
Interest cost	4,997	4,912
Expected return on plan assets	(5,708)	(6,254)	(7,772)
Recognized actuarial loss	3,072	3,164	1,107
Net periodic cost	3,287	2,873	(714)
Components of net periodic cost (benefit)
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 4,997	$ 4,912	$ 4,985