Other Comprehensive Income (Loss) (Net Accumulated Other Comprehensive Income (Loss)) (Detail) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	$ (823,000)	$ (2,970,000)
Other comprehensive income before reclassification, net of tax	2,793,000	4,309,000
Reclassifications from accumulated other comprehensive income, net of tax	176,000	11,000
Total other comprehensive income (loss)	2,969,000	4,320,000
Ending Balance	2,146,000	1,350,000
Unrealized Gains (Losses) on Investments Available-for-Sale
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	8,078,000	358,000
Other comprehensive income before reclassification, net of tax	2,793,000	4,309,000
Reclassifications from accumulated other comprehensive income, net of tax	0	0
Total other comprehensive income (loss)	2,793,000	4,309,000
Ending Balance	10,871,000	4,667,000
Defined Benefit Pension Plan
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(8,901,000)	(3,328,000)
Other comprehensive income before reclassification, net of tax	0	0
Reclassifications from accumulated other comprehensive income, net of tax	176,000	11,000
Total other comprehensive income (loss)	176,000	11,000
Ending Balance	$ (8,725,000)	$ (3,317,000)