Loan and Lease Finance Receivables and Allowance for Credit Losses - Schedule of Held-for-Investment and Held-for-Sale Loans, Individually Evaluated for Impairment by Class of Loans (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment	$ 108,390	$ 101,226
Unpaid Principal Balance	125,631	119,497
Related Allowance	2,332	2,968
Average Recorded Investment	110,479	107,665
Interest Income Recognized	2,300	2,225
With no related allowance recorded [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment	99,925	90,022
Unpaid Principal Balance	116,800	106,021
Related Allowance
Average Recorded Investment	102,609	95,339
Interest Income Recognized	2,227	2,225
With no related allowance recorded [Member] | Commercial and Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment	3,385	3,566
Unpaid Principal Balance	4,215	4,630
Related Allowance
Average Recorded Investment	3,766	4,649
Interest Income Recognized	43	93
With no related allowance recorded [Member] | Construction - speculative [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment	21,314	13,317
Unpaid Principal Balance	21,607	15,718
Related Allowance
Average Recorded Investment	21,650	15,434
Interest Income Recognized	311
With no related allowance recorded [Member] | Construction - non-speculative [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment	9,219	20,085
Unpaid Principal Balance	9,219	20,085
Related Allowance
Average Recorded Investment	9,219	16,437
Interest Income Recognized	574	1,123
With no related allowance recorded [Member] | Commercial real estate - owner occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment	13,478	13,567
Unpaid Principal Balance	14,569	14,013
Related Allowance
Average Recorded Investment	14,459	11,941
Interest Income Recognized	397	449
With no related allowance recorded [Member] | Commercial real estate - non-owner occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment	28,639	16,435
Unpaid Principal Balance	38,633	23,656
Related Allowance
Average Recorded Investment	29,801	21,096
Interest Income Recognized	670	67
With no related allowance recorded [Member] | Residential real estate (SFR 1-4) [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment	11,079	14,069
Unpaid Principal Balance	14,342	17,411
Related Allowance
Average Recorded Investment	11,292	15,120
Interest Income Recognized	54	47
With no related allowance recorded [Member] | Dairy and livestock [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment	12,406	8,879
Unpaid Principal Balance	13,756	10,358
Related Allowance
Average Recorded Investment	11,834	10,535
Interest Income Recognized	173	446
With no related allowance recorded [Member] | Municipal lease finance receivables [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment	263
Unpaid Principal Balance	263
Related Allowance
Average Recorded Investment	443
Interest Income Recognized	5
With no related allowance recorded [Member] | Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment	142	104
Unpaid Principal Balance	196	150
Related Allowance
Average Recorded Investment	145	127
With no related allowance recorded [Member] | Auto and equipment leases [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment
Unpaid Principal Balance
Related Allowance
Average Recorded Investment
Interest Income Recognized
With no related allowance recorded [Member] | Held-for-Sale Construction - Speculative [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment
Unpaid Principal Balance
Related Allowance
Average Recorded Investment
Interest Income Recognized
With a Related Allowance Recorded [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment	8,465	11,204
Unpaid Principal Balance	8,831	13,476
Related Allowance	2,332	2,968
Average Recorded Investment	7,870	12,326
Interest Income Recognized	73
With a Related Allowance Recorded [Member] | Commercial and Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment	304	1,388
Unpaid Principal Balance	327	1,410
Related Allowance	289	165
Average Recorded Investment	387	1,554
Interest Income Recognized
With a Related Allowance Recorded [Member] | Construction - speculative [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment
Unpaid Principal Balance
Related Allowance
Average Recorded Investment
Interest Income Recognized
With a Related Allowance Recorded [Member] | Construction - non-speculative [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment
Unpaid Principal Balance
Related Allowance
Average Recorded Investment
Interest Income Recognized
With a Related Allowance Recorded [Member] | Commercial real estate - owner occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment	19	3,900
Unpaid Principal Balance	19	3,900
Related Allowance	2	928
Average Recorded Investment	28	3,900
Interest Income Recognized
With a Related Allowance Recorded [Member] | Commercial real estate - non-owner occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment		83
Unpaid Principal Balance		85
Related Allowance		5
Average Recorded Investment		86
Interest Income Recognized
With a Related Allowance Recorded [Member] | Residential real estate (SFR 1-4) [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment	3,766	4,087
Unpaid Principal Balance	4,071	4,369
Related Allowance	434	406
Average Recorded Investment	3,363	3,967
Interest Income Recognized
With a Related Allowance Recorded [Member] | Dairy and livestock [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment	4,303	1,372
Unpaid Principal Balance	4,340	3,324
Related Allowance	1,596	1,372
Average Recorded Investment	4,017	2,402
Interest Income Recognized	73
With a Related Allowance Recorded [Member] | Municipal lease finance receivables [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment
Unpaid Principal Balance
Related Allowance
Average Recorded Investment
Interest Income Recognized
With a Related Allowance Recorded [Member] | Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment	73	270
Unpaid Principal Balance	74	278
Related Allowance	11	77
Average Recorded Investment	75	276
Interest Income Recognized
With a Related Allowance Recorded [Member] | Auto and equipment leases [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment		104
Unpaid Principal Balance		110
Related Allowance		15
Average Recorded Investment		141
Interest Income Recognized