Fair Values - Additional Information (Detail) (USD $)	9 Months Ended	12 Months Ended
	Sep. 30, 2013	Dec. 31, 2012 Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Promissory note discount rate	10.00%
Future cash flows discounted	5.99%
Number of municipal securities classified as Level 3		3
Carrying value of loans fully charged off	$ 0
Collateral Impaired Loans [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Collateral dependent impaired loans carrying amount	4,000,000
Fair value written down	3,500,000
Adjustment to ALLL	486,000
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-agency mortgage backed securities available for sale fair value		13,800,000
Level 3 [Member] | Obligations of States and Political Subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Municipal securities with a fair value		1,100,000
Level 3 [Member] | Municipal Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Municipal securities with a fair value		1,100,000
Level 2 [Member] | Municipal Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities transfer at fair value from Level 2 to Level 3		1,100,000
Securities transfer at fair value from level 3 to level 2	1,100,000
Level 2 [Member] | Non-agency Mortgage Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities transfer at fair value from Level 2 to Level 3		13,700,000
Securities transfer at fair value from level 3 to level 2	$ 749,000