Components of Net Periodic Benefit Cost (Net Periodic Benefit Cost (Increase)) (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Pension benefits [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Service cost	$ 0	$ 0
Interest cost	312	284
Expected return on plan assets	(612)	(633)
Amortization of prior service cost	0	0
Amortization of the net loss	236	194
Net periodic benefit (increase) cost	(64)	(155)
Other post-retirement benefits [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Service cost	38	42
Interest cost	284	281
Expected return on plan assets	0	0
Amortization of prior service cost	0	0
Amortization of the net loss	0	0
Net periodic benefit (increase) cost	$ 322	$ 323