Loans and Allowance for Credit Losses - Schedule of Past Due Financing Receivables (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	$ 18,879	$ 30,481
60-89 Days Past Due	3,451	5,294
Recorded Investment > 90 Days and Accruing	1,207	1,077
Nonaccrual	189,770	254,336
Total Past Due	213,307	291,188
Current	4,962,915	4,905,406
Commercial Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	815	2,691
60-89 Days Past Due	96	515
Recorded Investment > 90 Days and Accruing	11	322
Nonaccrual	31,408	36,766
Total Past Due	32,330	40,294
Current	1,365,552	1,296,526
Commercial Real Estate Construction Financing Receivable [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due		11
Nonaccrual	7,239	14,304
Total Past Due	7,239	14,315
Current	78,044	84,766
Commercial Real Estate Other Receivable [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	1,660	3,439
60-89 Days Past Due	213	665
Recorded Investment > 90 Days and Accruing	80	236
Nonaccrual	75,392	81,525
Total Past Due	77,345	85,865
Current	1,035,369	1,070,937
Consumer Heloc [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	496	961
60-89 Days Past Due	107	15
Recorded Investment > 90 Days and Accruing	112
Nonaccrual	1,447	1,720
Total Past Due	2,162	2,696
Current	242,434	255,418
Consumer, Auto [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	3,451	4,070
60-89 Days Past Due	669	881
Recorded Investment > 90 Days and Accruing	194	328
Nonaccrual	1,750	1,980
Total Past Due	6,064	7,259
Current	534,713	518,826
Consumer - Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	1,311	1,732
60-89 Days Past Due	287	403
Recorded Investment > 90 Days and Accruing	134	110
Nonaccrual	1,810	2,109
Total Past Due	3,542	4,354
Current	103,163	118,302
Residential [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	8,688	14,686
60-89 Days Past Due	1,518	1,874
Recorded Investment > 90 Days and Accruing	658	66
Nonaccrual	10,412	11,986
Total Past Due	21,276	28,612
Current	1,378,412	1,296,091
Covered Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	2,458	2,891
60-89 Days Past Due	561	941
Recorded Investment > 90 Days and Accruing	18	15
Nonaccrual	60,312	103,946
Total Past Due	63,349	107,793
Current	$ 225,228	$ 264,540