Loan and Lease Finance Receivables and Allowance for Loan Losses - Loans Modified as Troubled Debt Restructurings (Detail) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013 SecurityLoan	Jun. 30, 2012 SecurityLoan	Jun. 30, 2013 SecurityLoan	Jun. 30, 2012 SecurityLoan
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings, Number of Loans	4	15	10	19
Troubled debt restructurings, pre-modification outstanding recorded investment	$ 11,147,000	$ 20,197,000	$ 15,606,000	$ 23,551,000
Troubled debt restructurings, Post-Modification Outstanding Recorded Investment	11,147,000	20,197,000	15,606,000	23,551,000
Troubled debt restructurings, Outstanding Recorded Investment	10,960,000	19,461,000	15,606,000	22,810,000
Troubled debt restructurings, Financial Effect Resulting From Modifications	28,000	3,000	122,000	3,000
Non-Covered Loans [Member]
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings, Number of Loans	4	15	10	19
Troubled debt restructurings, pre-modification outstanding recorded investment	11,147,000	20,197,000	15,606,000	23,551,000
Troubled debt restructurings, Post-Modification Outstanding Recorded Investment	11,147,000	20,197,000	15,606,000	23,551,000
Troubled debt restructurings, Outstanding Recorded Investment	10,960,000	19,461,000	15,606,000	22,810,000
Troubled debt restructurings, Financial Effect Resulting From Modifications	28,000	3,000	122,000	3,000
Covered Loans [Member]
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings, Number of Loans
Troubled debt restructurings, pre-modification outstanding recorded investment
Troubled debt restructurings, Post-Modification Outstanding Recorded Investment
Troubled debt restructurings, Outstanding Recorded Investment
Troubled debt restructurings, Financial Effect Resulting From Modifications
Commercial and Industrial [Member] \| Interest rate reduction [Member]
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings, Number of Loans				1
Troubled debt restructurings, pre-modification outstanding recorded investment				80,000
Troubled debt restructurings, Post-Modification Outstanding Recorded Investment				80,000
Troubled debt restructurings, Outstanding Recorded Investment				74,000
Troubled debt restructurings, Financial Effect Resulting From Modifications
Commercial and Industrial [Member] \| Change in amortization period or maturity [Member]
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings, Number of Loans	1	7	3	8
Troubled debt restructurings, pre-modification outstanding recorded investment	28,000	1,677,000	231,000	4,131,000
Troubled debt restructurings, Post-Modification Outstanding Recorded Investment	28,000	1,677,000	231,000	4,131,000
Troubled debt restructurings, Outstanding Recorded Investment	28,000	1,350,000	207,000	3,808,000
Troubled debt restructurings, Financial Effect Resulting From Modifications	28,000	3,000	122,000	3,000
Commercial Real Estate Owner occupied [Member] \| Interest rate reduction [Member]
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings, Number of Loans
Troubled debt restructurings, pre-modification outstanding recorded investment
Troubled debt restructurings, Post-Modification Outstanding Recorded Investment
Troubled debt restructurings, Outstanding Recorded Investment
Troubled debt restructurings, Financial Effect Resulting From Modifications
Commercial Real Estate Owner occupied [Member] \| Change in amortization period or maturity [Member]
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings, Number of Loans		1	1	2
Troubled debt restructurings, pre-modification outstanding recorded investment		307,000	168,000	614,000
Troubled debt restructurings, Post-Modification Outstanding Recorded Investment		307,000	168,000	614,000
Troubled debt restructurings, Outstanding Recorded Investment		306,000	158,000	610,000
Troubled debt restructurings, Financial Effect Resulting From Modifications
Commercial real estate Non-owner occupied [Member] \| Interest rate reduction [Member]
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings, Number of Loans
Troubled debt restructurings, pre-modification outstanding recorded investment
Troubled debt restructurings, Post-Modification Outstanding Recorded Investment
Troubled debt restructurings, Outstanding Recorded Investment
Troubled debt restructurings, Financial Effect Resulting From Modifications
Commercial real estate Non-owner occupied [Member] \| Change in amortization period or maturity [Member]
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings, Number of Loans		1		2
Troubled debt restructurings, pre-modification outstanding recorded investment		3,378,000		3,891,000
Troubled debt restructurings, Post-Modification Outstanding Recorded Investment		3,378,000		3,891,000
Troubled debt restructurings, Outstanding Recorded Investment		3,359,000		3,865,000
Troubled debt restructurings, Financial Effect Resulting From Modifications
Commercial real estate Non-owner occupied [Member] \| Other [Member]
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings, Number of Loans		1		1
Troubled debt restructurings, pre-modification outstanding recorded investment		648,000		648,000
Troubled debt restructurings, Post-Modification Outstanding Recorded Investment		648,000		648,000
Troubled debt restructurings, Outstanding Recorded Investment		309,000		316,000
Troubled debt restructurings, Financial Effect Resulting From Modifications
Dairy & livestock and agribusiness [Member] \| Interest rate reduction [Member]
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings, Number of Loans
Troubled debt restructurings, pre-modification outstanding recorded investment
Troubled debt restructurings, Post-Modification Outstanding Recorded Investment
Troubled debt restructurings, Outstanding Recorded Investment
Troubled debt restructurings, Financial Effect Resulting From Modifications
Dairy & livestock and agribusiness [Member] \| Change in amortization period or maturity [Member]
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings, Number of Loans	3	4	6	4
Troubled debt restructurings, pre-modification outstanding recorded investment	11,119,000	3,221,000	15,207,000	3,221,000
Troubled debt restructurings, Post-Modification Outstanding Recorded Investment	11,119,000	3,221,000	15,207,000	3,221,000
Troubled debt restructurings, Outstanding Recorded Investment	10,932,000	3,221,000	15,136,000	3,221,000
Troubled debt restructurings, Financial Effect Resulting From Modifications
Construction Speculative [Member] \| Interest rate reduction [Member]
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings, Number of Loans
Troubled debt restructurings, pre-modification outstanding recorded investment
Troubled debt restructurings, Post-Modification Outstanding Recorded Investment
Troubled debt restructurings, Outstanding Recorded Investment
Troubled debt restructurings, Financial Effect Resulting From Modifications
Construction Speculative [Member] \| Change in amortization period or maturity [Member]
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings, Number of Loans		1		1
Troubled debt restructurings, pre-modification outstanding recorded investment		10,966,000		10,966,000
Troubled debt restructurings, Post-Modification Outstanding Recorded Investment		10,966,000		10,966,000
Troubled debt restructurings, Outstanding Recorded Investment		$ 10,916,000		$ 10,916,000