Components of Net Periodic Benefit Cost (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Defined benefit pension plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 2,597	$ 3,899
Interest cost	6,941	6,630
Expected return on plan assets	(8,003)	(7,329)
Amortization of prior service credit	(264)	(126)
Recognized actuarial loss	3,587	5,106
Net periodic benefit cost	4,858	8,180
Postretirement benefit plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	20	22
Interest cost	452	338
Recognized actuarial loss	75	40
Net periodic benefit cost	$ 547	$ 400