Employee Benefits - Components of Net Periodic Pension Cost and Other Changes in Plan Assets and Benefit (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Components of Net Periodic Pension Cost
Service cost—benefits earned during the period	$ 631	$ 708
Interest cost on projected benefit obligation	1,106	996
Expected return on plan assets	(1,735)	(1,565)
Amortization of prior service cost (credit)	(35)	(34)
Recognized net actuarial loss	209	588
Net Periodic Pension Expense	$ 176	$ 693