Net Periodic Benefit Cost (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Defined Benefit Plan Disclosure [Line Items]
Interest cost on projected benefit obligation	$ 390	$ 374	$ 1,163	$ 1,151
Expected return on plan assets	(425)	(220)	(1,259)	(874)
Recognized net actuarial loss	249	197	1,176	896
Net periodic benefit cost	$ 214	$ 351	$ 1,080	$ 1,173