Fair Value Measurements (Narrative) (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 30, 2012	Dec. 31, 2011
Percentage of securities using market-based information	97.00%
Percentage of securities using model-based techniques	3.00%
Minimum corporation reserves for commercial loan	$ 500
Change in unrealized gains or losses included in earnings relating to assets still held		37
Impaired loans, carrying amount	10,052
Allocated allowance for loan losses	4,701
Fair value of allocated allowance	5,987
Estimated costs to sell	636
Provision for fair value measurements included in allowance for loan losses	4,359
Carrying amount of OREO	8,995
Write down of OREO	5,795
Fair value of OREO	6,646
Estimated cost to sell OREO	851
Loss from OREO included in earnings	$ 3,200