Loans and Allowance for Credit Losses - Schedule of Past Due Financing Receivables (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	$ 20,854	$ 18,134
60-89 Days Past Due	5,000	4,884
Recorded Investment > 90 Days and Accruing	380	238
Nonaccrual	118,025	128,442
Total Past Due	144,259	151,698
Current	5,394,609	4,931,266
Commercial Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	1,045	1,532
60-89 Days Past Due	1,025	13
Recorded Investment > 90 Days and Accruing	2
Nonaccrual	30,305	28,635
Total Past Due	32,377	30,180
Current	1,466,456	1,343,235
Commercial Real Estate - Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	80
60-89 Days Past Due		139
Recorded Investment > 90 Days and Accruing
Nonaccrual	6,321	1,873
Total Past Due	6,401	2,012
Current	128,738	86,618
Commercial Real Estate - Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	229	1,017
60-89 Days Past Due	391	27
Recorded Investment > 90 Days and Accruing	78
Nonaccrual	44,323	50,490
Total Past Due	45,021	51,534
Current	1,174,540	1,020,726
Consumer Heloc [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	1,136	527
60-89 Days Past Due	118	119
Recorded Investment > 90 Days and Accruing
Nonaccrual	2,014	1,950
Total Past Due	3,268	2,596
Current	278,555	248,506
Consumer Auto [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	2,958	3,795
60-89 Days Past Due	639	716
Recorded Investment > 90 Days and Accruing	129	89
Nonaccrual	1,085	1,562
Total Past Due	4,811	6,162
Current	691,198	614,311
Consumer - Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	960	844
60-89 Days Past Due	269	317
Recorded Investment > 90 Days and Accruing	52	100
Nonaccrual	1,259	1,806
Total Past Due	2,540	3,067
Current	108,636	96,616
Residential [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	11,987	8,588
60-89 Days Past Due	2,145	2,823
Recorded Investment > 90 Days and Accruing	26	35
Nonaccrual	11,401	10,333
Total Past Due	25,559	21,779
Current	1,399,620	1,337,790
Covered Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	2,459	1,831
60-89 Days Past Due	413	730
Recorded Investment > 90 Days and Accruing	93	14
Nonaccrual	21,317	31,793
Total Past Due	24,282	34,368
Current	$ 146,866	$ 183,464