Consolidated Statements of Comprehensive Income (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Statement Of Income And Comprehensive Income [Abstract]
Income, Before Tax Amount	$ 6,367	$ 6,168	$ 13,475	$ 12,377
Net unrealized (losses) gains on available-for-sale investment securities, Before Tax Amount
Net unrealized holding (losses) gains arising during the period, Before Tax Amount	(9,201)	1,417	(10,605)	517
Less: reclassification adjustment for net gains on sales realized in net income, Before Tax Amount	(1,339)	(24)	(1,524)	(282)
Less: reclassification adjustment for other-than-temporary impairment on equity securities realized in net income, Before Tax Amount		6		9
Total net unrealized (losses) gains on available-for-sale investment securities, Before Tax Amount	(10,540)	1,399	(12,129)	244
Cash flow hedge derivative, Before Tax Amount
Net change in fair value of interest rate swap, Before Tax Amount	(119)	(563)	43	(389)
Less: reclassification adjustment for loss on termination of interest rate swap realized in net income, Before Tax Amount	1,866		1,866
Total cash flow hedge derivative, Before Tax Amount	1,747	(563)	1,909	(389)
Defined benefit pension plans, Before Tax Amount
Less: amortization of net loss included in net periodic pension costs, Before Tax Amount	349	292	641	589
Less: accretion of prior service cost included in net periodic pension costs, Before Tax Amount	(63)	(64)	(127)	(128)
Total defined benefit pension plans, Before Tax Amount	286	228	514	461
Other comprehensive (loss) income, Before Tax Amount	(8,507)	1,064	(9,706)	316
Total comprehensive (loss) income, Before Tax Amount	(2,140)	7,232	3,769	12,693
Income, Tax Expense (Benefit)	1,537	1,405	3,247	2,351
Net unrealized (losses) gains on available-for-sale investment securities, Tax Expense (Benefit)
Net unrealized holding (losses) gains arising during the period, Tax Expense (Benefit)	(3,221)	496	(3,712)	181
Less: reclassification adjustment for net gains on sales realized in net income, Tax Expense (Benefit)	(468)	(9)	(533)	(99)
Less: reclassification adjustment for other-than-temporary impairment on equity securities realized in net income, Tax Expense (Benefit)		2		3
Total net unrealized (losses) gains on available-for-sale investment securities, Tax Expense (Benefit)	(3,689)	489	(4,245)	85
Cash flow hedge derivative, Tax Expense (Benefit)
Net change in fair value of interest rate swap, Tax Expense (Benefit)	(42)	(197)	15	(136)
Less: reclassification adjustment for loss on termination of interest rate swap realized in net income, Tax Expense (Benefit)	653		653
Total cash flow hedge derivative, Tax Expense (Benefit)	611	(197)	668	(136)
Defined benefit pension plans, Tax Expense (Benefit)
Less: amortization of net loss included in net periodic pension costs, Tax Expense (Benefit)	122	102	224	206
Less: accretion of prior service cost included in net periodic pension costs, Tax Expense (Benefit)	(21)	(22)	(44)	(45)
Total defined benefit pension plans, Tax Expense (Benefit)	101	80	180	161
Other comprehensive (loss) income, Tax Expense (Benefit)	(2,977)	372	(3,397)	110
Total comprehensive (loss) income, Tax Expense (Benefit)	(1,440)	1,777	(150)	2,461
Income, Net of Tax Amount	4,830	4,763	10,228	10,026
Net unrealized (losses) gains on available-for-sale investment securities, Net of Tax Amount
Net unrealized holding (losses) gains arising during the period, Net of Tax Amount	(5,980)	921	(6,893)	336
Less: reclassification adjustment for net gains on sales realized in net income, Net of Tax Amount	(871)	(15)	(991)	(183)
Less: reclassification adjustment for other-than-temporary impairment on equity securities realized in net income, Net of Tax Amount		4		6
Total net unrealized (losses) gains on available-for-sale investment securities, Net of Tax Amount	(6,851)	910	(7,884)	159
Cash flow hedge derivative, Net of Tax Amount
Net change in fair value of interest rate swap, Net of Tax Amount	(77)	(366)	28	(253)
Less: reclassification adjustment for loss on termination of interest rate swap realized in net income, Net of Tax Amount	1,213		1,213
Total cash flow hedge derivative, Net of Tax Amount	1,136	(366)	1,241	(253)
Defined benefit pension plans, Net of Tax Amount
Less: amortization of net loss included in net periodic pension costs, Net of Tax Amount	227	190	417	383
Less: accretion of prior service cost included in net periodic pension costs, Net of Tax Amount	(42)	(42)	(83)	(83)
Total defined benefit pension plans, Net of Tax Amount	185	148	334	300
Other comprehensive (loss) income, Net of Tax Amount	(5,530)	692	(6,309)	206
Total comprehensive (loss) income, Net of Tax Amount	$ (700)	$ 5,455	$ 3,919	$ 10,232