Postretirement Benefits Other Than Pensions - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Defined Benefit Plan Disclosure [Line Items]
Accrued postretirement liability, current	$ 2,800,000
Employer expected contribution in 2014	2,800,000
Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Unrecognized prior service costs, before tax	742,000	768,000
Unrecognized prior service costs, net of tax	453,000	469,000
Unrecognized actuarial losses, before tax	(2,300,000)	(6,000,000)
Unrecognized actuarial losses, net of tax	(1,400,000)	(3,700,000)
Prior service costs expected to be recognized next fiscal year	65,000
Prior service costs expected to be recognized next fiscal year, net of tax	40,000
Actuarial losses expected to be recognized next fiscal year	75,000
Actuarial losses expected to be recognized next fiscal year, net of tax	46,000
Unfunded portion of liability	$ (37,230,000)	$ (37,428,000)