Retirement and Postretirement Benefits Other Than Pension Plans - Net Periodic Pension and Postretirement Benefit (Income) Expense (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Pension Plans, Defined Benefit [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Interest cost	$ 1,044	$ 993
Expected return on plan assets	(1,409)	(1,291)
Recognized net actuarial loss	148	318
Total net periodic pension (income) expense	(217)	20
Other Postretirement Benefit Plans, Defined Benefit [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Interest cost	55	64
Amortization of net actuarial loss	105	96
Amortization of prior service credit	(329)	(285)
Total net postretirement benefit (income) expense	$ (169)	$ (125)