Net Benefit Cost of Pension and Postretirement Benefit Plans (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Pension
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1,819	$ 2,331	$ 2,297
Interest cost	16,842	16,561	17,284
Expected return on plan assets	(23,122)	(20,245)	(19,998)
Net amortization and deferral	5,847	6,474	4,018
Curtailment gain		(197)	(37)
Settlement loss (gain)		106	(5)
Net benefit cost	1,386	5,030	3,559
Other Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	663	704	479
Interest cost	2,707	2,122	2,054
Expected return on plan assets
Net amortization and deferral	1,348	761	(45)
Curtailment gain
Settlement loss (gain)
Net benefit cost	$ 4,718	$ 3,587	$ 2,488