Fair Value Measurements and Disclosures - Carrying Value and Estimated Fair Value of Financial Assets and Financial Liabilities (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Financial Assets:
Cash and due from banks	$ 23,556,000	$ 36,264,000	$ 54,020,000	$ 36,929,000
Cash and due from banks, Fair Value	23,556,000	36,264,000	54,020,000
Available for sale securities	215,122,000	275,440,000	258,876,000
Held to maturity securities	17,784,000	11,142,000	7,125,000
Held to maturity securities, fair value	17,859,000	10,686,000	7,225,000
Other investments	2,962,000	3,262,000	3,450,000
Other investments, Fair Value	2,962,000	3,262,000	3,450,000
Federal Home Loan Bank stock	2,504,000	3,834,000	2,380,000
Federal Home Loan Bank stock, Fair Value	2,504,000	3,834,000	2,380,000
Loans, net	353,201,000	366,415,000	422,226,000
Loans, net, Fair Value	355,004,000	369,117,000	425,627,000
Other real estate	7,646,000	9,630,000	7,008,000
Other real estate, Fair Value	7,646,000	9,630,000	7,008,000
Cash surrender value of life insurance	18,145,000	17,456,000	16,861,000
Cash surrender value of life insurance, Fair Value	18,145,000	17,456,000	16,861,000
Deposits:
Non-interest bearing	103,607,000	107,117,000	102,609,000
Non-interest bearing, Fair Value	103,607,000	107,117,000	102,609,000
Interest bearing, Fair Value	289,466,000	322,535,000	376,209,000
Federal funds purchased and securities sold under agreements to repurchase	124,206,000	139,639,000	194,234,000
Federal funds purchased and securities sold under agreements to repurchase, Fair Value	124,206,000	139,639,000	194,234,000
Borrowings from Federal Home Loan Bank	40,720,000	79,051,000	10,271,000
Carrying Amount [Member]
Financial Assets:
Cash and due from banks	23,556,000	36,264,000	54,020,000
Available for sale securities	215,122,000	275,440,000	258,876,000
Held to maturity securities	17,784,000	11,142,000	7,125,000
Other investments	2,962,000	3,262,000	3,450,000
Federal Home Loan Bank stock	2,504,000	3,834,000	2,380,000
Loans, net	353,201,000	366,415,000	422,226,000
Other real estate	7,646,000	9,630,000	7,008,000
Cash surrender value of life insurance	18,145,000	17,456,000	16,861,000
Deposits:
Non-interest bearing	103,607,000	107,117,000	102,609,000
Interest bearing	289,107,000	321,441,000	373,110,000
Federal funds purchased and securities sold under agreements to repurchase	124,206,000	139,639,000	194,234,000
Borrowings from Federal Home Loan Bank	38,708,000	77,684,000	7,912,000
Level 1 [Member]
Financial Assets:
Cash and due from banks, Fair Value	23,556,000	36,264,000	54,020,000
Other investments, Fair Value	2,962,000	3,262,000	3,450,000
Deposits:
Non-interest bearing, Fair Value	103,607,000	107,117,000	102,609,000
Federal funds purchased and securities sold under agreements to repurchase, Fair Value	124,206,000	139,639,000	194,234,000
Level 2 [Member]
Financial Assets:
Available for sale securities	215,122,000	275,440,000	258,876,000
Held to maturity securities, fair value	17,859,000	10,686,000	7,225,000
Federal Home Loan Bank stock, Fair Value	2,504,000	3,834,000	2,380,000
Cash surrender value of life insurance, Fair Value	18,145,000	17,456,000	16,861,000
Deposits:
Borrowings from Federal Home Loan Bank	40,720,000	79,051,000	10,271,000
Level 3 [Member]
Financial Assets:
Loans, net, Fair Value	355,004,000	369,117,000	425,627,000
Other real estate	7,646,000	9,630,000	7,008,000	6,153,000
Other real estate, Fair Value	7,646,000	9,630,000	7,008,000
Deposits:
Interest bearing, Fair Value	$ 289,466,000	$ 322,535,000	$ 376,209,000