Loans and Allowance for Credit Losses - Schedule of Past Due Financing Receivables (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	$ 15,577	$ 18,134
60-89 Days Past Due	2,838	4,884
Recorded Investment > 90 Days and Accruing	193	238
Nonaccrual	112,103	128,442
Total Past Due	130,711	151,698
Current	4,941,570	4,931,266
Commercial Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	673	1,532
60-89 Days Past Due	12	13
Recorded Investment > 90 Days and Accruing
Nonaccrual	27,480	28,635
Total Past Due	28,165	30,180
Current	1,339,321	1,343,235
Commercial Real Estate-Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	763	0
60-89 Days Past Due	0	139
Recorded Investment > 90 Days and Accruing
Nonaccrual	2,515	1,873
Total Past Due	3,278	2,012
Current	89,258	86,618
Commercial Real Estate-Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	1,377	1,017
60-89 Days Past Due	687	27
Recorded Investment > 90 Days and Accruing	79	0
Nonaccrual	39,130	50,490
Total Past Due	41,273	51,534
Current	1,022,784	1,020,726
Consumer Heloc [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	517	527
60-89 Days Past Due	366	119
Recorded Investment > 90 Days and Accruing
Nonaccrual	2,144	1,950
Total Past Due	3,027	2,596
Current	248,273	248,506
Consumer Auto [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	2,688	3,795
60-89 Days Past Due	369	716
Recorded Investment > 90 Days and Accruing	53	89
Nonaccrual	1,406	1,562
Total Past Due	4,516	6,162
Current	645,164	614,311
Consumer - Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	834	844
60-89 Days Past Due	97	317
Recorded Investment > 90 Days and Accruing	19	100
Nonaccrual	1,578	1,806
Total Past Due	2,528	3,067
Current	94,300	96,616
Residential [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	7,106	8,588
60-89 Days Past Due	1,004	2,823
Recorded Investment > 90 Days and Accruing	42	35
Nonaccrual	10,561	10,333
Total Past Due	18,713	21,779
Current	1,337,520	1,337,790
Covered Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	1,619	1,831
60-89 Days Past Due	303	730
Recorded Investment > 90 Days and Accruing	0	14
Nonaccrual	27,289	31,793
Total Past Due	29,211	34,368
Current	$ 164,950	$ 183,464