Fair Value Information - Assets and Liabilities Measured at Fair Value on Non-Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Description of assets
Impaired loans-non-covered	$ 3,288	$ 3,930
OREO-non-covered		336
OREO-covered		467
Total assets	3,288	4,733
Level 1 [Member]
Description of assets
Impaired loans-non-covered
OREO-non-covered
OREO-covered
Total assets
Level 2 [Member]
Description of assets
Impaired loans-non-covered
OREO-non-covered
OREO-covered
Total assets
Level 3 [Member]
Description of assets
Impaired loans-non-covered	13,857	12,460
OREO-non-covered		3,008
OREO-covered		1,067
Total assets	13,857	16,535
Carrying Value [Member]
Description of assets
Impaired loans-non-covered	13,857	12,460
OREO-non-covered		3,008
OREO-covered		1,067
Total assets	$ 13,857	$ 16,535