Loan and Lease Finance Receivables and Allowance for Loan Losses - Schedule of Recorded Investment in Non-Covered Past Due and Nonaccrual Loans and Loans Past Due by Class of Loans (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
30-59 Days Past Due	$ 487,000	$ 2,600
Current	23,700	40,100
Non-Covered Loans [Member]
30-59 Days Past Due	1,193	422
60-89 Days Past Due	494	465
90+ Days Past Due and Accruing
Total Past Due and Accruing	1,687	887
Nonaccrual	49,484	57,997
Current	3,239,300	3,200,354
Total Loans and Financing Receivables	3,290,471	3,259,238
Non-Covered Loans [Member] | Commercial and Industrial [Member]
30-59 Days Past Due	417	233
60-89 Days Past Due		457
90+ Days Past Due and Accruing
Total Past Due and Accruing	417	690
Nonaccrual	3,734	3,136
Current	506,415	543,596
Total Loans and Financing Receivables	510,566	547,422
Non-Covered Loans [Member] | Commercial Real Estate Owner occupied [Member]
30-59 Days Past Due
60-89 Days Past Due
90+ Days Past Due and Accruing
Total Past Due and Accruing
Nonaccrual	4,180	5,415
Current	721,376	698,552
Total Loans and Financing Receivables	725,556	703,967
Non-Covered Loans [Member] | Commercial real estate Non-owner occupied [Member]
30-59 Days Past Due	772
60-89 Days Past Due	243
90+ Days Past Due and Accruing
Total Past Due and Accruing	1,015
Nonaccrual	13,649	15,624
Current	1,386,195	1,270,516
Total Loans and Financing Receivables	1,400,859	1,286,140
Non-Covered Loans [Member] | Construction Speculative [Member]
30-59 Days Past Due
60-89 Days Past Due
90+ Days Past Due and Accruing
Total Past Due and Accruing
Nonaccrual	10,368	10,663
Current	16,758	27,231
Total Loans and Financing Receivables	27,126	37,894
Non-Covered Loans [Member] | Construction Non-speculative [Member]
30-59 Days Past Due
60-89 Days Past Due
90+ Days Past Due and Accruing
Total Past Due and Accruing
Nonaccrual
Current	20,522	21,827
Total Loans and Financing Receivables	20,522	21,827
Non-Covered Loans [Member] | SFR Mortgage [Member]
30-59 Days Past Due		107
60-89 Days Past Due
90+ Days Past Due and Accruing
Total Past Due and Accruing		107
Nonaccrual	10,421	13,102
Current	181,709	146,079
Total Loans and Financing Receivables	192,130	159,288
Non-Covered Loans [Member] | Dairy & Livestock and Agribusiness [Member]
30-59 Days Past Due
60-89 Days Past Due
90+ Days Past Due and Accruing
Total Past Due and Accruing
Nonaccrual	6,973	9,842
Current	254,665	326,818
Total Loans and Financing Receivables	261,638	336,660
Non-Covered Loans [Member] | Municipal lease finance receivables [Member]
30-59 Days Past Due
60-89 Days Past Due
90+ Days Past Due and Accruing
Total Past Due and Accruing
Nonaccrual
Current	99,188	105,767
Total Loans and Financing Receivables	99,188	105,767
Non-Covered Loans [Member] | Consumer and Other Loans [Member]
30-59 Days Past Due	4	82
60-89 Days Past Due	251	8
90+ Days Past Due and Accruing
Total Past Due and Accruing	255	90
Nonaccrual	159	215
Current	52,472	59,968
Total Loans and Financing Receivables	$ 52,886	$ 60,273