Past Due, Non-Accrual and Current Loans (Excluding PCI Loans) (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due Loans	$ 47,119	$ 37,585
Accruing Loans 90 Days Or More Past Due	2,493	4,016
Non-Accrual Loans (thousand)	121,371	124,264
Total Past Due Loans	170,983	165,865
Current Non-PCI Loans	9,703,602	9,361,932
Total Non-PCI Loans	9,874,585	9,527,797
Commercial Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due Loans	6,236	15,767
Accruing Loans 90 Days Or More Past Due	1,245	2,245
Non-Accrual Loans (thousand)	73,680	62,060
Total Past Due Loans	81,161	80,072
Current Non-PCI Loans	4,069,094	3,905,020
Total Non-PCI Loans	4,150,255	3,985,092
Consumer Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due Loans	6,463	8,975
Accruing Loans 90 Days Or More Past Due	197	351
Non-Accrual Loans (thousand)	3,831	3,910
Total Past Due Loans	10,491	13,236
Current Non-PCI Loans	1,383,826	1,365,492
Total Non-PCI Loans	1,394,317	1,378,728
Other Consumer | Commercial Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due Loans	17,459
Non-Accrual Loans (thousand)	12,296
Total Past Due Loans	29,755
Current Non-PCI Loans	1,817,895
Total Non-PCI Loans	1,847,650
Other Consumer | Consumer Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due Loans	237	192
Accruing Loans 90 Days Or More Past Due	17	35
Non-Accrual Loans (thousand)	659	749
Total Past Due Loans	913	976
Current Non-PCI Loans	158,754	135,658
Total Non-PCI Loans	159,667	136,634
Commercial Real Estate | Commercial Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due Loans	6,236	13,115
Accruing Loans 90 Days Or More Past Due	221	422
Non-Accrual Loans (thousand)	58,541	42,186
Total Past Due Loans	64,998	55,723
Current Non-PCI Loans	3,687,965	3,518,366
Total Non-PCI Loans	3,752,963	3,574,089
Construction | Commercial Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due Loans		2,652
Accruing Loans 90 Days Or More Past Due	1,024	1,823
Non-Accrual Loans (thousand)	15,139	19,874
Total Past Due Loans	16,163	24,349
Current Non-PCI Loans	381,129	386,654
Total Non-PCI Loans	397,292	411,003
Residential Mortgage | Consumer Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due Loans	16,961	8,496
Accruing Loans 90 Days Or More Past Due	1,051	763
Non-Accrual Loans (thousand)	31,564	31,646
Total Past Due Loans	49,576	40,905
Current Non-PCI Loans	2,432,787	2,244,685
Total Non-PCI Loans	2,482,363	2,285,590
Home Equity | Consumer Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due Loans	466	989
Accruing Loans 90 Days Or More Past Due		13
Non-Accrual Loans (thousand)	2,828	2,700
Total Past Due Loans	3,294	3,702
Current Non-PCI Loans	442,108	465,902
Total Non-PCI Loans	445,402	469,604
Automobile Loans | Consumer Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due Loans	5,760	7,794
Accruing Loans 90 Days Or More Past Due	180	303
Non-Accrual Loans (thousand)	344	461
Total Past Due Loans	6,284	8,558
Current Non-PCI Loans	782,964	763,932
Total Non-PCI Loans	789,248	772,490
Commercial and Industrial | Commercial Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due Loans		4,347
Accruing Loans 90 Days Or More Past Due		657
Non-Accrual Loans (thousand)		26,648
Total Past Due Loans		31,652
Current Non-PCI Loans		1,846,735
Total Non-PCI Loans		$ 1,878,387