Loans - Allowance for Loan and Lease Losses and Recorded Investment in Loans (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 30, 2013	Dec. 31, 2012
Allowance for Loan and Lease Losses:
Balance at beginning of year	$ 6,950	$ 6,711
Charge-offs	(324)	(817)
Recoveries	126	132
Provision	800	924
Balance at end of year	7,552	6,950
Ending balance: Individually evaluated for impairment	1,174	1,226
Ending balance: Collectively evaluated for impairment	6,378	5,724
Ending balance: Loans acquired with deteriorated credit quality
Loans:
Ending Balance	642,353	623,530
Ending balance: Individually evaluated for impairment	4,848	5,271
Ending balance: Collectively evaluated for impairment	637,505	618,259
Ending balance: Loans acquired with deteriorated credit quality
Commercial [Member]
Allowance for Loan and Lease Losses:
Balance at beginning of year	799	793
Charge-offs		(78)
Recoveries		1
Provision	400	83
Balance at end of year	1,199	799
Ending balance: Individually evaluated for impairment	612	351
Ending balance: Collectively evaluated for impairment	587	448
Ending balance: Loans acquired with deteriorated credit quality
Loans:
Ending Balance	97,318	91,724
Ending balance: Individually evaluated for impairment	937	655
Ending balance: Collectively evaluated for impairment	96,381	91,069
Ending balance: Loans acquired with deteriorated credit quality
Commercial Real Estate [Member]
Allowance for Loan and Lease Losses:
Balance at beginning of year	2,304	2,294
Charge-offs		(33)
Recoveries		6
Provision		37
Balance at end of year	2,304	2,304
Ending balance: Individually evaluated for impairment	300	550
Ending balance: Collectively evaluated for impairment	2,004	1,754
Ending balance: Loans acquired with deteriorated credit quality
Loans:
Ending Balance	226,032	217,496
Ending balance: Individually evaluated for impairment	1,757	2,160
Ending balance: Collectively evaluated for impairment	224,275	215,336
Ending balance: Loans acquired with deteriorated credit quality
Consumer [Member]
Allowance for Loan and Lease Losses:
Balance at beginning of year	540	450
Charge-offs	(72)	(235)
Recoveries	20	57
Provision	76	268
Balance at end of year	564	540
Ending balance: Individually evaluated for impairment
Ending balance: Collectively evaluated for impairment	564	540
Ending balance: Loans acquired with deteriorated credit quality
Loans:
Ending Balance	49,732	49,199
Ending balance: Individually evaluated for impairment	52	31
Ending balance: Collectively evaluated for impairment	49,680	49,168
Ending balance: Loans acquired with deteriorated credit quality
Residential [Member]
Allowance for Loan and Lease Losses:
Balance at beginning of year	2,981	2,855
Charge-offs	(207)	(431)
Recoveries	106	67
Provision	212	490
Balance at end of year	3,092	2,981
Ending balance: Individually evaluated for impairment	262	325
Ending balance: Collectively evaluated for impairment	2,830	2,656
Ending balance: Loans acquired with deteriorated credit quality
Loans:
Ending Balance	266,240	261,912
Ending balance: Individually evaluated for impairment	2,102	2,425
Ending balance: Collectively evaluated for impairment	264,138	259,487
Ending balance: Loans acquired with deteriorated credit quality
Credit Card Portfolio Segment [Member]
Allowance for Loan and Lease Losses:
Balance at beginning of year	326	319
Charge-offs	(45)	(40)
Recoveries		1
Provision	112	46
Balance at end of year	393	326
Ending balance: Individually evaluated for impairment
Ending balance: Collectively evaluated for impairment	393	326
Ending balance: Loans acquired with deteriorated credit quality
Loans:
Ending Balance	3,031	3,199
Ending balance: Individually evaluated for impairment
Ending balance: Collectively evaluated for impairment	3,031	3,199
Ending balance: Loans acquired with deteriorated credit quality
Unallocated [Member]
Allowance for Loan and Lease Losses:
Balance at beginning of year
Charge-offs
Recoveries
Provision
Balance at end of year
Ending balance: Individually evaluated for impairment
Ending balance: Collectively evaluated for impairment
Ending balance: Loans acquired with deteriorated credit quality
Loans:
Ending Balance
Ending balance: Individually evaluated for impairment
Ending balance: Collectively evaluated for impairment
Ending balance: Loans acquired with deteriorated credit quality