Pension Plans - Funded Status and Accrued Pension Cost (Detail) - Pension Plan [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
CHANGE IN BENEFIT OBLIGATION:
Benefit obligation at beginning of year	$ 87,236	$ 94,113
Interest cost	3,173	3,423	$ 3,577
Actuarial (gain) loss	304	(3,377)
Benefits paid	(5,353)	(6,923)
Benefit obligation at end of year	85,360	87,236	94,113
CHANGE IN PLAN ASSETS:
Fair value of plan assets at beginning of year	65,439	75,260
Actual return (loss) on plan assets	5,360	(2,898)
Benefits paid	(5,353)	(6,923)
Fair value of plan assets at end of year	65,446	65,439	$ 75,260
Funded status and accrued pension cost	$ (19,914)	$ (21,797)