Loans - Impaired Loans (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 30, 2013	Dec. 31, 2012
Financing Receivable, Impaired [Line Items]
With an allowance recorded, Recorded Investment	$ 4,848
Recorded Investment		5,271
With an allowance recorded, Unpaid Principal Balance	4,848
Unpaid Principal Balance		5,271
With no related allowance recorded, Related Allowance	1,174	1,226
With an allowance recorded, Average Recorded Investment	4,894
Average Recorded Investment		5,068
With an allowance recorded, Interest Income Recognized	56
Interest Income Recognized		175
Commercial Real Estate - Construction [Member]
Financing Receivable, Impaired [Line Items]
With an allowance recorded, Recorded Investment
With an allowance recorded, Unpaid Principal Balance
With no related allowance recorded, Related Allowance
With an allowance recorded, Average Recorded Investment
With an allowance recorded, Interest Income Recognized
Commercial Real Estate -Other [Member]
Financing Receivable, Impaired [Line Items]
With an allowance recorded, Recorded Investment	1,443	2,015
With an allowance recorded, Unpaid Principal Balance	1,443	2,015
With no related allowance recorded, Related Allowance	300	550
With an allowance recorded, Average Recorded Investment	1,445	2,104
With an allowance recorded, Interest Income Recognized	38	114
Commercial [Member]
Financing Receivable, Impaired [Line Items]
With an allowance recorded, Recorded Investment	612	351
With an allowance recorded, Unpaid Principal Balance	612	351
With no related allowance recorded, Related Allowance	612	351
With an allowance recorded, Average Recorded Investment	532	351
With an allowance recorded, Interest Income Recognized	12	17
Residential Real Estate [Member]
Financing Receivable, Impaired [Line Items]
With no related allowance recorded, Recorded Investment	1,437	928
With an allowance recorded, Recorded Investment	665	1,497
With no related allowance recorded, Unpaid Principal Balance	1,437	928
With an allowance recorded, Unpaid Principal Balance	665	1,497
With no related allowance recorded, Related Allowance	262	325
With no related allowance recorded, Average Recorded Investment	1,047	1,152
With an allowance recorded, Average Recorded Investment	1,233	1,040
With no related allowance recorded, Interest Income Recognized
With an allowance recorded, Interest Income Recognized	6	44
Commercial Real Estate [Member]
Financing Receivable, Impaired [Line Items]
With no related allowance recorded, Recorded Investment	314	145
With no related allowance recorded, Unpaid Principal Balance	314	145
With no related allowance recorded, Related Allowance
With no related allowance recorded, Average Recorded Investment	287	201
With no related allowance recorded, Interest Income Recognized
Commercial [Member]
Financing Receivable, Impaired [Line Items]
With no related allowance recorded, Recorded Investment	325	304
With no related allowance recorded, Unpaid Principal Balance	325	304
With no related allowance recorded, Related Allowance
With no related allowance recorded, Average Recorded Investment	280	152
With no related allowance recorded, Interest Income Recognized
Consumer - TERI [Member]
Financing Receivable, Impaired [Line Items]
With no related allowance recorded, Recorded Investment	38	19
With no related allowance recorded, Unpaid Principal Balance	38	19
With no related allowance recorded, Related Allowance
With no related allowance recorded, Average Recorded Investment	61	48
With no related allowance recorded, Interest Income Recognized
Consumer - Other [Member]
Financing Receivable, Impaired [Line Items]
With no related allowance recorded, Recorded Investment	4	9
With no related allowance recorded, Unpaid Principal Balance	4	9
With no related allowance recorded, Related Allowance
With no related allowance recorded, Average Recorded Investment	3	5
With no related allowance recorded, Interest Income Recognized
Consumer - Auto [Member]
Financing Receivable, Impaired [Line Items]
With no related allowance recorded, Recorded Investment	10	3
With no related allowance recorded, Unpaid Principal Balance	10	3
With no related allowance recorded, Related Allowance
With no related allowance recorded, Average Recorded Investment	6	15
With no related allowance recorded, Interest Income Recognized
Commercial Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	1,757	2,160
Unpaid Principal Balance	1,757	2,160
With no related allowance recorded, Related Allowance	300	550
Average Recorded Investment	1,732	2,305
Interest Income Recognized	38	114
Commercial [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	937	655
Unpaid Principal Balance	937	655
With no related allowance recorded, Related Allowance	612	351
Average Recorded Investment	812	503
Interest Income Recognized	12	17
Consumer [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	52	31
Unpaid Principal Balance	52	31
With no related allowance recorded, Related Allowance
Average Recorded Investment	70	68
Interest Income Recognized
Residential [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	2,102	2,425
Unpaid Principal Balance	2,102	2,425
With no related allowance recorded, Related Allowance	262	325
Average Recorded Investment	2,280	2,192
Interest Income Recognized	$ 6	$ 44