Net Accumulated Other Comprehensive Income (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Comprehensive Income [Line Items]
Beginning Balance	$ 358
Other comprehensive income before reclassification, net of tax	4,309
Reclassifications from accumulated other comprehensive income, net of tax	0	33
Current period change in other comprehensive income, net of tax	4,309	(1,798)
Ending Balance	4,667
Beginning Balance	(3,328)
Other comprehensive income before reclassification, net of tax	0
Reclassifications from accumulated other comprehensive income, net of tax	11	218
Current period change in other comprehensive income, net of tax	11	218
Ending Balance	(3,317)
Beginning Balance	(2,970)	11,312
Other comprehensive income before reclassification, net of tax	4,309	(1,831)
Reclassifications from accumulated other comprehensive income, net of tax	11	251
Current period change in other comprehensive income, net of tax	4,320	(1,580)
Ending Balance	1,350	9,732
Unrealized Gains (Losses) on Investments Available-for-Sale
Comprehensive Income [Line Items]
Beginning Balance		20,258
Other comprehensive income before reclassification, net of tax		(1,831)
Reclassifications from accumulated other comprehensive income, net of tax		33
Current period change in other comprehensive income, net of tax		(1,798)
Ending Balance		18,460
Defined Benefit Pension Plan
Comprehensive Income [Line Items]
Beginning Balance		(8,946)
Other comprehensive income before reclassification, net of tax		0
Reclassifications from accumulated other comprehensive income, net of tax		218
Current period change in other comprehensive income, net of tax		218
Ending Balance		$ (8,728)