Loans - Past Due, Non-Accrual and Current Non-Covered Loans (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due Loans	$ 49,686	$ 37,585
Accruing Loans 90 Days Or More Past Due	8,665	4,016
Non-Accrual Loans	131,808	124,264
Total Past Due Loans	190,159	165,865
Current Non-PCI Loans	9,664,976	9,361,932
Total Non-PCI Loans	9,855,135	9,527,797
Commercial real estate loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due Loans	19,930	15,767
Accruing Loans 90 Days Or More Past Due	5,525	2,245
Non-Accrual Loans	73,430	62,060
Total Past Due Loans	98,885	80,072
Current Non-PCI Loans	4,073,054	3,905,020
Total Non-PCI Loans	4,171,939	3,985,092
Consumer loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due Loans	7,227	8,975
Accruing Loans 90 Days Or More Past Due	501	351
Non-Accrual Loans	3,331	3,910
Total Past Due Loans	11,059	13,236
Current Non-PCI Loans	1,393,767	1,365,492
Total Non-PCI Loans	1,404,826	1,378,728
Commercial and industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due Loans	3,578	4,347
Accruing Loans 90 Days Or More Past Due	283	657
Non-Accrual Loans	22,424	26,648
Total Past Due Loans	26,285	31,652
Current Non-PCI Loans	1,806,458	1,846,735
Total Non-PCI Loans	1,832,743	1,878,387
Commercial real estate [Member] | Commercial real estate loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due Loans	13,245	13,115
Accruing Loans 90 Days Or More Past Due	2,950	422
Non-Accrual Loans	58,625	42,186
Total Past Due Loans	74,820	55,723
Current Non-PCI Loans	3,697,264	3,518,366
Total Non-PCI Loans	3,772,084	3,574,089
Construction [Member] | Commercial real estate loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due Loans	6,685	2,652
Accruing Loans 90 Days Or More Past Due	2,575	1,823
Non-Accrual Loans	14,805	19,874
Total Past Due Loans	24,065	24,349
Current Non-PCI Loans	375,790	386,654
Total Non-PCI Loans	399,855	411,003
Residential mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due Loans	18,951	8,496
Accruing Loans 90 Days Or More Past Due	2,356	763
Non-Accrual Loans	32,623	31,646
Total Past Due Loans	53,930	40,905
Current Non-PCI Loans	2,391,697	2,244,685
Total Non-PCI Loans	2,445,627	2,285,590
Home equity [Member] | Consumer loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due Loans	702	989
Accruing Loans 90 Days Or More Past Due		13
Non-Accrual Loans	2,398	2,700
Total Past Due Loans	3,100	3,702
Current Non-PCI Loans	435,781	465,902
Total Non-PCI Loans	438,881	469,604
Automobile [Member] | Consumer loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due Loans	5,443	7,794
Accruing Loans 90 Days Or More Past Due	469	303
Non-Accrual Loans	305	461
Total Past Due Loans	6,217	8,558
Current Non-PCI Loans	780,311	763,932
Total Non-PCI Loans	786,528	772,490
Other consumer [Member] | Consumer loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due Loans	1,082	192
Accruing Loans 90 Days Or More Past Due	32	35
Non-Accrual Loans	628	749
Total Past Due Loans	1,742	976
Current Non-PCI Loans	177,675	135,658
Total Non-PCI Loans	$ 179,417	$ 136,634