Loans - Schedule of Loan Portfolio Non-Covered and Covered PCI Loans and Non-PCI Loans (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	$ 11,613,664	$ 11,471,447
Covered loans	80,930	96,165
Total loans	11,694,594	11,567,612
Commercial Real Estate Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	5,497,539	5,410,906
Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	1,624,846	1,565,492
Covered loans	959	799
Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	2,019,099	1,995,084
Covered loans	20,839	26,249
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	5,083,744	4,981,675
Covered loans	52,196	61,494
Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	413,795	429,231
Residential Mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	2,472,180	2,499,965
Covered loans	6,936	7,623
Home Equity [Member] | Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	440,006	449,009
Automobile [Member] | Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	957,036	901,399
Other Consumer [Member] | Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	227,804	215,084
Non-PCI Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	10,951,995	10,761,344
Covered loans	0
Total loans	10,951,995	10,761,344
Non-PCI Loans [Member] | Commercial Real Estate Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	5,052,919	4,928,797
Non-PCI Loans [Member] | Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	1,587,461	1,527,172
Covered loans
Non-PCI Loans [Member] | Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	1,853,938	1,820,136
Covered loans
Non-PCI Loans [Member] | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	4,661,294	4,521,920
Covered loans
Non-PCI Loans [Member] | Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	391,625	406,877
Non-PCI Loans [Member] | Residential Mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	2,457,677	2,485,239
Covered loans
Non-PCI Loans [Member] | Home Equity [Member] | Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	402,793	410,875
Non-PCI Loans [Member] | Automobile [Member] | Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	957,036	901,399
Non-PCI Loans [Member] | Other Consumer [Member] | Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	227,632	214,898
PCI Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	661,669	710,103
Covered loans	80,930	96,165
Total loans	742,599	806,268
PCI Loans [Member] | Commercial Real Estate Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	444,620	482,109
PCI Loans [Member] | Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	37,385	38,320
Covered loans	959	799
PCI Loans [Member] | Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	165,161	174,948
Covered loans	20,839	26,249
PCI Loans [Member] | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	422,450	459,755
Covered loans	52,196	61,494
PCI Loans [Member] | Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	22,170	22,354
PCI Loans [Member] | Residential Mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	14,503	14,726
Covered loans	6,936	7,623
PCI Loans [Member] | Home Equity [Member] | Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	37,213	38,134
PCI Loans [Member] | Automobile [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	0	0
PCI Loans [Member] | Other Consumer [Member] | Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	$ 172	$ 186