Change in Accumulated Other Comprehensive Income (Loss) - Components of Accumulated Other Comprehensive Income (Loss) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	$ (21,294)	$ 12,943
Other comprehensive income (loss) before reclassifications	9,145	(4,827)
Less: Amounts reclassified from accumulated other comprehensive income (loss)	(358)	(1,019)
Total other comprehensive (loss) income	8,787	(5,846)
Ending Balance	(12,507)	7,097
Net Unrealized (Losses) Gains on Investment Securities Available-for-Sale [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(20,822)	13,415
Other comprehensive income (loss) before reclassifications	9,145	(4,827)
Less: Amounts reclassified from accumulated other comprehensive income (loss)	(358)	(1,019)
Total other comprehensive (loss) income	8,787	(5,846)
Ending Balance	(12,035)	7,569
Net Unrealized Losses on Defined Benefit Pension Plan [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(472)	(472)
Other comprehensive income (loss) before reclassifications
Less: Amounts reclassified from accumulated other comprehensive income (loss)
Total other comprehensive (loss) income
Ending Balance	$ (472)	$ (472)