Employer Sponsored Benefit Plan (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	$ 614	$ 648	$ 1,841	$ 1,944
Expected return on assets	(673)	(640)	(2,019)	(1,920)
Amortization of actuarial loss	267	224	801	671
Net periodic benefit cost	$ 208	$ 232	$ 623	$ 695