Fair Value Measurements (Narrative) (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Percentage of securities using market-based information	97.00%
Percentage of securities using model-based techniques	3.00%
Change in discount rate	1.00%
One percent change in affecting fair value of debt obligation, amount	$ 3,000
One percent change in affecting fair value of debt obligation, percent	4.00%
Minimum corporation reserves for commercial loan	500
Change in unrealized gains or losses included in earnings relating to assets still held	212	66
Impaired loans, carrying amount	20,921
Allocated allowance for loan losses	5,197
Fair value of allocated allowance	17,496
Estimated costs to sell	1,772
Provision for fair value measurements included in allowance for loan losses	2,416
Carrying amount of OREO	21,637
Written down of OREO	16,959
Fair value of OREO	19,311
Estimated cost to sell OREO	2,352
Loss from OREO included in earnings	4,677
Impairment of credit loss recognized in earnings	(212)
Impairment loss,recognized in other comprehensive income	$ 269
Short-term borrowings approximate fair value for amounts that mature, days, less than	90 days
Minimum [Member]
Valuation of investment securities basis spread on index	15.00%
Maximum [Member]
Valuation of investment securities basis spread on index	20.00%