Components of Periodic Benefit Costs for Defined-Benefit Pension, Postretirement Healthcare and Supplemental Retirement Plan (Parenthetical) (Detail) (Actuarial Loss, USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Actuarial Loss
Defined Benefit Plan Disclosure [Line Items]
Amortization of net actuarial loss	$ 622	$ 523	$ 1,245	$ 1,050