Components of Net Periodic Benefit Cost (Net Periodic Benefit Cost (Increase)) (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Pension benefits [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Service cost	$ 0	$ 0	$ 0	$ 0
Interest cost	312	284	936	852
Expected return on plan assets	(612)	(632)	(1,836)	(1,898)
Amortization of prior service cost	0	0	0	0
Amortization of the net loss	236	193	708	581
Net periodic benefit (increase) cost	(64)	(155)	(192)	(465)
Other post-retirement benefits [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Service cost	37	42	112	126
Interest cost	285	280	854	842
Expected return on plan assets	0	0	0	0
Amortization of prior service cost	0	0	0	0
Amortization of the net loss	0	0	0	0
Net periodic benefit (increase) cost	$ 322	$ 322	$ 966	$ 968