Loan and Lease Finance Receivables and Allowance for Loan 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	9 Months Ended	12 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment, Total non-covered impaired loans	$ 108,679	$ 108,390
Unpaid Principal Balance, Total non-covered impaired loans	126,530	125,631
Related Allowance, Total non-covered impaired loans	3,485	2,332
Average Recorded Investment, Total non-covered impaired loans	112,594	110,479
Interest Income Recognized, Total non-covered impaired loans	2,393	2,300
Recorded Investment, With no related allowance recorded	91,026	99,925
Unpaid Principal Balance, With no related allowance recorded	108,025	116,800
Related Allowance, With no related allowance recorded
Average Recorded Investment, With no related allowance recorded	94,289	102,609
Interest Income Recognized, With no related allowance recorded	2,156	2,227
Recorded Investment, With a related allowance recorded	17,653	8,465
Unpaid Principal Balance, With a related allowance recorded	18,505	8,831
Related Allowance, With a related allowance recorded	3,485	2,332
Average Recorded Investment, With a related allowance recorded	18,305	7,870
Interest Income Recognized, With a related allowance recorded	237	73
Commercial and Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment, With no related allowance recorded	4,595	3,385
Unpaid Principal Balance, With no related allowance recorded	6,020	4,215
Related Allowance, With no related allowance recorded
Average Recorded Investment, With no related allowance recorded	5,131	3,766
Interest Income Recognized, With no related allowance recorded	161	43
Recorded Investment, With a related allowance recorded	388	304
Unpaid Principal Balance, With a related allowance recorded	408	327
Related Allowance, With a related allowance recorded	387	289
Average Recorded Investment, With a related allowance recorded	417	387
Interest Income Recognized, With a related allowance recorded
Commercial Real Estate Owner occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment, With no related allowance recorded	13,361	13,478
Unpaid Principal Balance, With no related allowance recorded	14,412	14,569
Related Allowance, With no related allowance recorded
Average Recorded Investment, With no related allowance recorded	13,635	14,459
Interest Income Recognized, With no related allowance recorded	494	397
Recorded Investment, With a related allowance recorded	7	19
Unpaid Principal Balance, With a related allowance recorded	9	19
Related Allowance, With a related allowance recorded	1	2
Average Recorded Investment, With a related allowance recorded	11	28
Interest Income Recognized, With a related allowance recorded
Commercial real estate Non-owner occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment, With no related allowance recorded	25,631	28,639
Unpaid Principal Balance, With no related allowance recorded	36,851	38,633
Related Allowance, With no related allowance recorded
Average Recorded Investment, With no related allowance recorded	26,838	29,801
Interest Income Recognized, With no related allowance recorded	553	670
Recorded Investment, With a related allowance recorded
Unpaid Principal Balance, With a related allowance recorded
Related Allowance, With a related allowance recorded
Average Recorded Investment, With a related allowance recorded
Interest Income Recognized, With a related allowance recorded
Construction Speculative [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment, With no related allowance recorded	10,369	21,314
Unpaid Principal Balance, With no related allowance recorded	10,956	21,607
Related Allowance, With no related allowance recorded
Average Recorded Investment, With no related allowance recorded	10,522	21,650
Interest Income Recognized, With no related allowance recorded		311
Recorded Investment, With a related allowance recorded	7,651
Unpaid Principal Balance, With a related allowance recorded	7,651
Related Allowance, With a related allowance recorded	144
Average Recorded Investment, With a related allowance recorded	7,651
Interest Income Recognized, With a related allowance recorded	232
Construction Non-speculative [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment, With no related allowance recorded	9,219	9,219
Unpaid Principal Balance, With no related allowance recorded	9,219	9,219
Related Allowance, With no related allowance recorded
Average Recorded Investment, With no related allowance recorded	9,219	9,219
Interest Income Recognized, With no related allowance recorded	428	574
Recorded Investment, With a related allowance recorded
Unpaid Principal Balance, With a related allowance recorded
Related Allowance, With a related allowance recorded
Average Recorded Investment, With a related allowance recorded
Interest Income Recognized, With a related allowance recorded
SFR Mortgage [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment, With no related allowance recorded	10,156	11,079
Unpaid Principal Balance, With no related allowance recorded	11,838	14,342
Related Allowance, With no related allowance recorded
Average Recorded Investment, With no related allowance recorded	9,487	11,292
Interest Income Recognized, With no related allowance recorded	75	54
Recorded Investment, With a related allowance recorded	2,649	3,766
Unpaid Principal Balance, With a related allowance recorded	2,764	4,071
Related Allowance, With a related allowance recorded	290	434
Average Recorded Investment, With a related allowance recorded	2,636	3,363
Interest Income Recognized, With a related allowance recorded	5
Dairy & Livestock and Agribusiness [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment, With no related allowance recorded	17,553	12,406
Unpaid Principal Balance, With no related allowance recorded	18,515	13,756
Related Allowance, With no related allowance recorded
Average Recorded Investment, With no related allowance recorded	19,308	11,834
Interest Income Recognized, With no related allowance recorded	445	173
Recorded Investment, With a related allowance recorded	6,941	4,303
Unpaid Principal Balance, With a related allowance recorded	7,654	4,340
Related Allowance, With a related allowance recorded	2,658	1,596
Average Recorded Investment, With a related allowance recorded	7,571	4,017
Interest Income Recognized, With a related allowance recorded		73
Municipal lease finance receivables [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment, With no related allowance recorded		263
Unpaid Principal Balance, With no related allowance recorded		263
Related Allowance, With no related allowance recorded
Average Recorded Investment, With no related allowance recorded		443
Interest Income Recognized, With no related allowance recorded		5
Recorded Investment, With a related allowance recorded
Unpaid Principal Balance, With a related allowance recorded
Related Allowance, With a related allowance recorded
Average Recorded Investment, With a related allowance recorded
Interest Income Recognized, With a related allowance recorded
Consumer and Other Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment, With no related allowance recorded	142	142
Unpaid Principal Balance, With no related allowance recorded	214	196
Related Allowance, With no related allowance recorded
Average Recorded Investment, With no related allowance recorded	149	145
Interest Income Recognized, With no related allowance recorded
Recorded Investment, With a related allowance recorded	17	73
Unpaid Principal Balance, With a related allowance recorded	19	74
Related Allowance, With a related allowance recorded	5	11
Average Recorded Investment, With a related allowance recorded	19	75
Interest Income Recognized, With a related allowance recorded