Fair Value Information - Assets and Liabilities Measured at Fair Value on Non-Recurring Basis (Detail) (Fair Value on Non-Recurring Basis [Member], USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Description of assets
Total assets	$ 3,159	$ 4,733
Impaired loans-non-covered [Member] \| Commercial and Industrial [Member]
Description of assets
Total assets	627	409
Impaired loans-non-covered [Member] \| Commercial Real Estate [Member]
Description of assets
Total assets		1,441
Impaired loans-non-covered [Member] \| Construction [Member]
Description of assets
Total assets
Impaired loans-non-covered [Member] \| SFR Mortgage [Member]
Description of assets
Total assets		473
Impaired loans-non-covered [Member] \| Dairy & Livestock and Agribusiness [Member]
Description of assets
Total assets	2,096	1,597
Impaired loans-non-covered [Member] \| Consumer and Other Loans [Member]
Description of assets
Total assets	2	10
Non-Covered Loans [Member]
Description of assets
Total assets		336
Covered Loans [Member]
Description of assets
Total assets	434	467
Level 1 [Member]
Description of assets
Total assets
Level 1 [Member] \| Impaired loans-non-covered [Member] \| Commercial and Industrial [Member]
Description of assets
Total assets
Level 1 [Member] \| Impaired loans-non-covered [Member] \| Commercial Real Estate [Member]
Description of assets
Total assets
Level 1 [Member] \| Impaired loans-non-covered [Member] \| Construction [Member]
Description of assets
Total assets
Level 1 [Member] \| Impaired loans-non-covered [Member] \| SFR Mortgage [Member]
Description of assets
Total assets
Level 1 [Member] \| Impaired loans-non-covered [Member] \| Dairy & Livestock and Agribusiness [Member]
Description of assets
Total assets
Level 1 [Member] \| Impaired loans-non-covered [Member] \| Consumer and Other Loans [Member]
Description of assets
Total assets
Level 1 [Member] \| Non-Covered Loans [Member]
Description of assets
Total assets
Level 1 [Member] \| Covered Loans [Member]
Description of assets
Total assets
Level 2 [Member]
Description of assets
Total assets
Level 2 [Member] \| Impaired loans-non-covered [Member] \| Commercial and Industrial [Member]
Description of assets
Total assets
Level 2 [Member] \| Impaired loans-non-covered [Member] \| Commercial Real Estate [Member]
Description of assets
Total assets
Level 2 [Member] \| Impaired loans-non-covered [Member] \| Construction [Member]
Description of assets
Total assets
Level 2 [Member] \| Impaired loans-non-covered [Member] \| SFR Mortgage [Member]
Description of assets
Total assets
Level 2 [Member] \| Impaired loans-non-covered [Member] \| Dairy & Livestock and Agribusiness [Member]
Description of assets
Total assets
Level 2 [Member] \| Impaired loans-non-covered [Member] \| Consumer and Other Loans [Member]
Description of assets
Total assets
Level 2 [Member] \| Non-Covered Loans [Member]
Description of assets
Total assets
Level 2 [Member] \| Covered Loans [Member]
Description of assets
Total assets
Level 3 [Member]
Description of assets
Total assets	12,934	16,535
Level 3 [Member] \| Impaired loans-non-covered [Member] \| Commercial and Industrial [Member]
Description of assets
Total assets	529	1,134
Level 3 [Member] \| Impaired loans-non-covered [Member] \| Commercial Real Estate [Member]
Description of assets
Total assets		4,146
Level 3 [Member] \| Impaired loans-non-covered [Member] \| Construction [Member]
Description of assets
Total assets
Level 3 [Member] \| Impaired loans-non-covered [Member] \| SFR Mortgage [Member]
Description of assets
Total assets		2,807
Level 3 [Member] \| Impaired loans-non-covered [Member] \| Dairy & Livestock and Agribusiness [Member]
Description of assets
Total assets	11,899	4,303
Level 3 [Member] \| Impaired loans-non-covered [Member] \| Consumer and Other Loans [Member]
Description of assets
Total assets	2	70
Level 3 [Member] \| Non-Covered Loans [Member]
Description of assets
Total assets		3,008
Level 3 [Member] \| Covered Loans [Member]
Description of assets
Total assets	504	1,067
Carrying Value [Member]
Description of assets
Total assets	12,934	16,535
Carrying Value [Member] \| Impaired loans-non-covered [Member] \| Commercial and Industrial [Member]
Description of assets
Total assets	529	1,134
Carrying Value [Member] \| Impaired loans-non-covered [Member] \| Commercial Real Estate [Member]
Description of assets
Total assets		4,146
Carrying Value [Member] \| Impaired loans-non-covered [Member] \| Construction [Member]
Description of assets
Total assets
Carrying Value [Member] \| Impaired loans-non-covered [Member] \| SFR Mortgage [Member]
Description of assets
Total assets		2,807
Carrying Value [Member] \| Impaired loans-non-covered [Member] \| Dairy & Livestock and Agribusiness [Member]
Description of assets
Total assets	11,899	4,303
Carrying Value [Member] \| Impaired loans-non-covered [Member] \| Consumer and Other Loans [Member]
Description of assets
Total assets	2	70
Carrying Value [Member] \| Non-Covered Loans [Member]
Description of assets
Total assets		3,008
Carrying Value [Member] \| Covered Loans [Member]
Description of assets
Total assets	$ 504	$ 1,067