Pensions and Other Post-retirement Benefits - Components of Net Periodic Benefit Cost (Credit) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 11,517	$ 9,425	$ 11,132
Interest cost	18,314	19,340	17,934
Expected return on plan assets	(34,130)	(32,944)	(30,884)
Amortization of transition amounts	2	2	3
Amortization of prior service cost (credit)	66	84	102
Recognized net actuarial losses	15,545	8,639	13,323
Settlement loss	641	290	658
Termination benefits	0	0	0
Net periodic benefit cost	11,955	4,836	12,268
Other Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	444	538	687
Interest cost	863	1,107	1,050
Expected return on plan assets	0	0	0
Amortization of transition amounts	0	0	0
Amortization of prior service cost (credit)	(335)	(335)	(424)
Recognized net actuarial losses	27	182	552
Settlement loss	0	0	0
Termination benefits	0	0	0
Net periodic benefit cost	$ 999	$ 1,492	$ 1,865