Components of Net Periodic Benefit Cost (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 2,481	$ 2,784
Interest cost	4,891	4,468
Expected return on plan assets	(8,251)	(7,725)
Amortization of prior service cost	21	26
Recognized net actuarial losses	2,203	3,327
Settlement / Curtailment loss	57	0
Net periodic benefit cost	1,402	2,880
Other Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	156	172
Interest cost	299	262
Expected return on plan assets	0	0
Amortization of prior service cost	(84)	(106)
Recognized net actuarial losses	83	138
Settlement / Curtailment loss	0	0
Net periodic benefit cost	$ 454	$ 466