Loans - Summary of Troubled Debt Restructurings, Included in Purchased Non-Covered Loans, by Collateral Types (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
Financing Receivable, Modifications [Line Items]
Troubled debt restructuring loans	$ 21,200	$ 20,900	$ 23,300
Purchased Non-Covered Loans [Member]
Financing Receivable, Modifications [Line Items]
Troubled debt restructuring loans	5,191	5,938
Purchased Non-Covered Loans [Member] | Accruing Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	22	24
Troubled debt restructuring loans	5,191	5,938
Purchased Non-Covered Loans [Member] | Accruing Loans [Member] | Warehouse [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts
Troubled debt restructuring loans
Purchased Non-Covered Loans [Member] | Accruing Loans [Member] | Raw Land [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	5	6
Troubled debt restructuring loans	1,988	2,640
Purchased Non-Covered Loans [Member] | Accruing Loans [Member] | Office [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	1	1
Troubled debt restructuring loans	798	803
Purchased Non-Covered Loans [Member] | Accruing Loans [Member] | Retail, Including Strip Centers [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	1	2
Troubled debt restructuring loans	164	425
Purchased Non-Covered Loans [Member] | Accruing Loans [Member] | 1-4 Family Residential [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	15	13
Troubled debt restructuring loans	2,241	2,053
Purchased Non-Covered Loans [Member] | Accruing Loans [Member] | Automobile/Equipment/Inventory [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts		2
Troubled debt restructuring loans		17
Purchased Non-Covered Loans [Member] | Non-Accruing Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	11	10
Troubled debt restructuring loans	1,268	1,212
Purchased Non-Covered Loans [Member] | Non-Accruing Loans [Member] | Warehouse [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	1	1
Troubled debt restructuring loans	467	468
Purchased Non-Covered Loans [Member] | Non-Accruing Loans [Member] | Raw Land [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts
Troubled debt restructuring loans
Purchased Non-Covered Loans [Member] | Non-Accruing Loans [Member] | Office [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts
Troubled debt restructuring loans
Purchased Non-Covered Loans [Member] | Non-Accruing Loans [Member] | Retail, Including Strip Centers [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	1
Troubled debt restructuring loans	259
Purchased Non-Covered Loans [Member] | Non-Accruing Loans [Member] | 1-4 Family Residential [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	6	8
Troubled debt restructuring loans	519	738
Purchased Non-Covered Loans [Member] | Non-Accruing Loans [Member] | Automobile/Equipment/Inventory [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	3	1
Troubled debt restructuring loans	$ 23	$ 6