Net Accumulated Other Comprehensive Income (Loss) (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
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			$ 13,248	$ (2,620)
Period change, net of tax	1,739	7,744	1,329	8,104
Ending Balance	14,577	5,484	14,577	5,484
Unrealized Gain(Loss) on Investements Available-for-Sale
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			20,006	3,764
Period change, net of tax			909	7,747
Ending Balance	20,915	11,511	20,915	11,511
Pension Plans, Defined Benefit
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			(6,758)	(6,384)
Period change, net of tax			420	357
Ending Balance	$ (6,338)	$ (6,027)	$ (6,338)	$ (6,027)