Fair Values - Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis (Detail) (Fair Value, Measurements, Nonrecurring [Member], USD $)	Sep. 30, 2013	Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	$ 31,205,000	$ 34,406,000
Foreclosed assets	3,549,000	6,970,000
Total	34,754,000	41,376,000
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	0	0
Foreclosed assets	0	0
Total	0	0
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	0	0
Foreclosed assets	0	0
Total	0	0
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	31,205,000	34,406,000
Foreclosed assets	3,549,000	6,970,000
Total	$ 34,754,000	$ 41,376,000