Loans - Summary of Troubled Debt Restructurings Included in Purchased Non-Covered Loans, by Concessions Made 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] | Forbearance of Principal [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	1	1
Troubled debt restructuring loans	299	300
Purchased Non-Covered Loans [Member] | Accruing Loans [Member] | Forgiveness of Principal [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] | Payment Modification Only [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	1	2
Troubled debt restructuring loans	61	75
Purchased Non-Covered Loans [Member] | Accruing Loans [Member] | Rate Reduction Only [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	12	11
Troubled debt restructuring loans	2,354	2,170
Purchased Non-Covered Loans [Member] | Accruing Loans [Member] | Rate Reduction, Forbearance of Principal [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	7	8
Troubled debt restructuring loans	2,313	2,968
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] | Forbearance of Principal [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts
Troubled debt restructuring loans
Purchased Non-Covered Loans [Member] | Non-Accruing Loans [Member] | Forgiveness of Principal [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	1
Troubled debt restructuring loans	259
Purchased Non-Covered Loans [Member] | Non-Accruing Loans [Member] | Payment Modification Only [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	1
Troubled debt restructuring loans	13
Purchased Non-Covered Loans [Member] | Non-Accruing Loans [Member] | Rate Reduction Only [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	7	8
Troubled debt restructuring loans	491	707
Purchased Non-Covered Loans [Member] | Non-Accruing Loans [Member] | Rate Reduction, Forbearance of Principal [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	2	2
Troubled debt restructuring loans	$ 505	$ 505