Components of Net Periodic Pension and Other Post-retirement Benefit Cost (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit cost	$ 0
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	527	691
Interest cost	1,966	1,666
Expected return on plan assets	(2,825)	(2,584)
Amortization of prior service cost	228	248
Amortization of actuarial loss	1,358	1,790
Special termination benefits		2,052
Net periodic benefit cost	1,254	3,863
Other Post-Retirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	239	216
Interest cost	534	477
Amortization of prior service cost	172	303
Amortization of actuarial loss	24	88
Special termination benefits		162
Net periodic benefit cost	$ 969	$ 1,246