Accumulated Other Comprehensive (Loss) Income - Amounts Reclassified Out of Each Component of Accumulated Comprehensive (Loss) Income (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amortization of net loss included in net periodic pension costs	$ 167	$ 349	$ 331	$ 641
Net unrealized holding gains (losses) on available-for-sale investment securities:	415	1,339	557	1,524
Accretion of prior service cost included in net periodic pension costs	(69)	(63)	(144)	(127)
Income before income taxes	6,627	6,367	14,358	13,475
Tax (expense) benefit	(1,547)	(1,537)	(3,552)	(3,247)
Net of tax	5,080	4,830	10,806	10,228
Amount Reclassified from Accumulated Other Comprehensive (Loss) Income [Member] | Net Unrealized Holding (Losses) Gains on Available-for-Sale Investment Securities [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net unrealized holding gains (losses) on available-for-sale investment securities:	415	1,339	557	1,524
Income before income taxes	415	1,339	557	1,524
Tax (expense) benefit	(145)	(468)	(195)	(533)
Net of tax	270	871	362	991
Amount Reclassified from Accumulated Other Comprehensive (Loss) Income [Member] | Net Change Related to Derivative Used for Cash Flow Hedge [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net loss on interest rate swap		(1,866)		(1,866)
Income before income taxes		(1,866)		(1,866)
Tax (expense) benefit		653		653
Net of tax		(1,213)		(1,213)
Amount Reclassified from Accumulated Other Comprehensive (Loss) Income [Member] | Net Change Related to Defined Benefit Pension Plan [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amortization of net loss included in net periodic pension costs	(167)	(349)	(331)	(641)
Accretion of prior service cost included in net periodic pension costs	69	63	144	127
Income before income taxes	(98)	(286)	(187)	(514)
Tax (expense) benefit	34	101	65	180
Net of tax	$ (64)	$ (185)	$ (122)	$ (334)