Components of Net Periodic Benefit Cost (Credit) (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 11,132	$ 9,511	$ 8,674
Interest cost	17,934	19,018	19,531
Expected return on plan assets	(30,884)	(32,328)	(34,125)
Amortization of transition amounts	3	2	4
Amortization of prior service cost	102	101	104
Recognized net actuarial losses	13,323	6,235	793
Curtailment loss	658	747	52
Termination benefits	0	387	0
Net periodic benefit cost (credit)	12,268	3,673	(4,967)
Other Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	687	694	785
Interest cost	1,050	1,265	1,501
Expected return on plan assets	0	0	0
Amortization of transition amounts	0	0	0
Amortization of prior service cost	(424)	(454)	(455)
Recognized net actuarial losses	552	529	710
Curtailment loss	0	0	0
Termination benefits	0	0	0
Net periodic benefit cost (credit)	$ 1,865	$ 2,034	$ 2,541