Components of Net Periodic Pension Benefit of Pension Plan And Excess Pension Plan (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 502	$ 598	$ 1,032	$ 1,196
Expected return on assets	(1,110)	(1,147)	(2,257)	(2,294)
Recognized net actuarial loss	663	476	1,358	952
Amortization of prior service (credit)	(389)	(346)	(777)	(692)
Net periodic pension (benefit)	$ (334)	$ (419)	$ (644)	$ (838)