Allowance for Loan Losses - Impaired Financing Receivables (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Financing Receivable, Impaired [Line Items]
Impaired financing receivables, with no related allowance recorded, Recorded Investment	$ 9,289		$ 8,718
Impaired financing receivables, with no related allowance recorded, Unpaid Principal Balance	11,256		10,142
Impaired financing receivables, with no related allowance recorded, Related Allowance
Impaired financing receivables, with an allowance recorded, Recorded Investment	9,990		9,339
Impaired financing receivables, with an allowance recorded, Unpaid Principal Balance	11,527		10,954
Impaired financing receivables, with an allowance recorded, Related Allowance	3,034		2,509
Impaired financing receivables, Recorded Investment, Total	19,279		18,057
Impaired financing receivables, Unpaid Principal Balance, Total	22,783		21,096
Impaired financing receivables, Related Allowance, Total	3,034		2,509
Impaired financing receivables, Average Recorded Investment, Total	18,668	25,325
Impaired financing receivables, Interest Income Recognized, Total	304	421
Commercial and Agriculture [Member]
Financing Receivable, Impaired [Line Items]
Impaired financing receivables, with no related allowance recorded, Recorded Investment	1,491		1,525
Impaired financing receivables, with no related allowance recorded, Unpaid Principal Balance	1,792		1,657
Impaired financing receivables, with no related allowance recorded, Related Allowance
Impaired financing receivables, with an allowance recorded, Recorded Investment	3,260		2,344
Impaired financing receivables, with an allowance recorded, Unpaid Principal Balance	3,408		2,437
Impaired financing receivables, with an allowance recorded, Related Allowance	1,172		1,262
Impaired financing receivables, Recorded Investment, Total	4,751		3,869
Impaired financing receivables, Unpaid Principal Balance, Total	5,200		4,094
Impaired financing receivables, Related Allowance, Total	1,172		1,262
Impaired financing receivables, Average Recorded Investment, Total	4,310	5,301
Impaired financing receivables, Interest Income Recognized, Total	65	68
Commercial Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Impaired financing receivables, with no related allowance recorded, Recorded Investment	7,517		5,983
Impaired financing receivables, with no related allowance recorded, Unpaid Principal Balance	7,909		6,214
Impaired financing receivables, with no related allowance recorded, Related Allowance
Impaired financing receivables, with an allowance recorded, Recorded Investment	3,212		4,192
Impaired financing receivables, with an allowance recorded, Unpaid Principal Balance	3,391		4,496
Impaired financing receivables, with an allowance recorded, Related Allowance	1,092		445
Impaired financing receivables, Recorded Investment, Total	10,729		10,175
Impaired financing receivables, Unpaid Principal Balance, Total	11,300		10,710
Impaired financing receivables, Related Allowance, Total	1,092		445
Impaired financing receivables, Average Recorded Investment, Total	10,569	13,584
Impaired financing receivables, Interest Income Recognized, Total	147	205
Residential Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Impaired financing receivables, with no related allowance recorded, Recorded Investment	274		1,202
Impaired financing receivables, with no related allowance recorded, Unpaid Principal Balance	1,548		2,263
Impaired financing receivables, with no related allowance recorded, Related Allowance
Impaired financing receivables, with an allowance recorded, Recorded Investment	3,518		2,803
Impaired financing receivables, with an allowance recorded, Unpaid Principal Balance	4,728		4,021
Impaired financing receivables, with an allowance recorded, Related Allowance	770		802
Impaired financing receivables, Recorded Investment, Total	3,792		4,005
Impaired financing receivables, Unpaid Principal Balance, Total	6,276		6,284
Impaired financing receivables, Related Allowance, Total	770		802
Impaired financing receivables, Average Recorded Investment, Total	3,782	5,876
Impaired financing receivables, Interest Income Recognized, Total	92	143
Real Estate Construction [Member]
Financing Receivable, Impaired [Line Items]
Impaired financing receivables, with no related allowance recorded, Recorded Investment
Impaired financing receivables, with no related allowance recorded, Unpaid Principal Balance
Impaired financing receivables, with no related allowance recorded, Related Allowance
Impaired financing receivables, with an allowance recorded, Recorded Investment
Impaired financing receivables, with an allowance recorded, Unpaid Principal Balance
Impaired financing receivables, with an allowance recorded, Related Allowance
Impaired financing receivables, Recorded Investment, Total
Impaired financing receivables, Unpaid Principal Balance, Total
Impaired financing receivables, Related Allowance, Total
Impaired financing receivables, Average Recorded Investment, Total		514
Impaired financing receivables, Interest Income Recognized, Total		5
Consumer and Other [Member]
Financing Receivable, Impaired [Line Items]
Impaired financing receivables, with no related allowance recorded, Recorded Investment	7		8
Impaired financing receivables, with no related allowance recorded, Unpaid Principal Balance	7		8
Impaired financing receivables, with no related allowance recorded, Related Allowance
Impaired financing receivables, with an allowance recorded, Recorded Investment
Impaired financing receivables, with an allowance recorded, Unpaid Principal Balance
Impaired financing receivables, with an allowance recorded, Related Allowance
Impaired financing receivables, Recorded Investment, Total	7		8
Impaired financing receivables, Unpaid Principal Balance, Total	7		8
Impaired financing receivables, Related Allowance, Total
Impaired financing receivables, Average Recorded Investment, Total	$ 7	$ 50