Net Periodic Benefit Cost (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Defined Benefit Plan Disclosure [Line Items]
Interest cost on projected benefit obligation	$ 386	$ 389	$ 773	$ 777
Expected return on plan assets	(417)	(327)	(834)	(654)
Recognized net actuarial loss	563	349	927	699
Net periodic benefit cost	$ 532	$ 411	$ 866	$ 822