Loans - Summary of Troubled Debt Restructurings, Excluding Purchased Non-Covered and Covered Loans, by Collateral Types (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2013
Financing Receivable, Modifications [Line Items]
Troubled debt restructuring loans	$ 21,100	$ 20,900	$ 20,600
Excluding Purchased Non-Covered and Covered Loans [Member]
Financing Receivable, Modifications [Line Items]
Troubled debt restructuring loans	17,337	17,214	18,015
Excluding Purchased Non-Covered and Covered Loans [Member] | Accruing Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	86	72	61
Troubled debt restructuring loans	17,337	17,214	18,015
Excluding Purchased Non-Covered and Covered Loans [Member] | Accruing Loans [Member] | Warehouse [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	4	4	2
Troubled debt restructuring loans	1,385	1,346	345
Excluding Purchased Non-Covered and Covered Loans [Member] | Accruing Loans [Member] | Raw Land [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	5	11	3
Troubled debt restructuring loans	1,279	2,345	1,354
Excluding Purchased Non-Covered and Covered Loans [Member] | Accruing Loans [Member] | Agricultural Land [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	2		1
Troubled debt restructuring loans	374		66
Excluding Purchased Non-Covered and Covered Loans [Member] | Accruing Loans [Member] | Hotel & Motel [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	3	3	3
Troubled debt restructuring loans	2,101	2,185	2,233
Excluding Purchased Non-Covered and Covered Loans [Member] | Accruing Loans [Member] | Office [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	4	4	4
Troubled debt restructuring loans	1,644	1,909	2,085
Excluding Purchased Non-Covered and Covered Loans [Member] | Accruing Loans [Member] | Retail, Including Strip Centers [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	5	4	6
Troubled debt restructuring loans	1,722	1,095	2,800
Excluding Purchased Non-Covered and Covered Loans [Member] | Accruing Loans [Member] | 1-4 Family Residential [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	46	36	34
Troubled debt restructuring loans	8,144	7,747	8,061
Excluding Purchased Non-Covered and Covered Loans [Member] | Accruing Loans [Member] | Church [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	1
Troubled debt restructuring loans	364
Excluding Purchased Non-Covered and Covered Loans [Member] | Accruing Loans [Member] | Life Insurance Policy [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts		1	1
Troubled debt restructuring loans		250	249
Excluding Purchased Non-Covered and Covered Loans [Member] | Accruing Loans [Member] | Automobile/Equipment/Inventory [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	15	8	5
Troubled debt restructuring loans	84	92	522
Excluding Purchased Non-Covered and Covered Loans [Member] | Accruing Loans [Member] | Unsecured [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	1	1	2
Troubled debt restructuring loans	240	245	300
Excluding Purchased Non-Covered and Covered Loans [Member] | Non-Accruing Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	22	20	9
Troubled debt restructuring loans	3,743	3,683	2,568
Excluding Purchased Non-Covered and Covered Loans [Member] | Non-Accruing Loans [Member] | Warehouse [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	2	2	2
Troubled debt restructuring loans	469	592	1,493
Excluding Purchased Non-Covered and Covered Loans [Member] | Non-Accruing Loans [Member] | Raw Land [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	1	2	1
Troubled debt restructuring loans	29	32	29
Excluding Purchased Non-Covered and Covered Loans [Member] | Non-Accruing Loans [Member] | Retail, Including Strip Centers [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	2	2
Troubled debt restructuring loans	1,682	1,680
Excluding Purchased Non-Covered and Covered Loans [Member] | Non-Accruing Loans [Member] | 1-4 Family Residential [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	10	9	6
Troubled debt restructuring loans	1,063	852	1,046
Excluding Purchased Non-Covered and Covered Loans [Member] | Non-Accruing Loans [Member] | Automobile/Equipment/Inventory [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	7	4
Troubled debt restructuring loans	500	479
Excluding Purchased Non-Covered and Covered Loans [Member] | Non-Accruing Loans [Member] | Unsecured [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts		1
Troubled debt restructuring loans		$ 48