Loans - Schedule of Loan Portfolio Non-Covered and Covered PCI Loans and Non-PCI Loans (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	$ 10,741,208	$ 10,842,125
Covered loans	141,817	180,674
Total loans	10,883,025	11,022,799
Commercial real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	4,864,603	4,843,153
Consumer loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	1,475,233	1,451,717
Covered loans	1,714	2,306
Commercial and industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	1,988,404	2,084,826
Covered loans	32,990	46,517
Commercial real estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	4,437,712	4,417,709
Covered loans	95,164	120,268
Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	426,891	425,444
Covered loans	3,029	1,924
Residential mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	2,412,968	2,462,429
Covered loans	8,920	9,659
Home equity [Member] | Consumer loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	455,166	485,458
Automobile [Member] | Consumer loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	835,271	786,528
Other consumer [Member] | Consumer loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	184,796	179,731
Non-PCI Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	9,931,620	9,855,135
Covered loans
Total loans	9,931,620	9,855,135
Non-PCI Loans [Member] | Commercial real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	4,297,576	4,171,939
Non-PCI Loans [Member] | Consumer loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	1,435,342	1,404,826
Covered loans
Non-PCI Loans [Member] | Commercial and industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	1,800,818	1,832,743
Covered loans
Non-PCI Loans [Member] | Commercial real estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	3,893,492	3,772,084
Covered loans
Non-PCI Loans [Member] | Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	404,084	399,855
Covered loans
Non-PCI Loans [Member] | Residential mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	2,397,884	2,445,627
Covered loans
Non-PCI Loans [Member] | Home equity [Member] | Consumer loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	415,501	438,881
Non-PCI Loans [Member] | Automobile [Member] | Consumer loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	835,271	786,528
Non-PCI Loans [Member] | Other consumer [Member] | Consumer loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	184,570	179,417
PCI Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	809,588	986,990
Covered loans	141,817	180,674
Total loans	951,405	1,167,664
PCI Loans [Member] | Commercial real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	567,027	671,214
PCI Loans [Member] | Consumer loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	39,891	46,891
Covered loans	1,714	2,306
PCI Loans [Member] | Commercial and industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	187,586	252,083
Covered loans	32,990	46,517
PCI Loans [Member] | Commercial real estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	544,220	645,625
Covered loans	95,164	120,268
PCI Loans [Member] | Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	22,807	25,589
Covered loans	3,029	1,924
PCI Loans [Member] | Residential mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	15,084	16,802
Covered loans	8,920	9,659
PCI Loans [Member] | Home equity [Member] | Consumer loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	39,665	46,577
PCI Loans [Member] | Automobile [Member] | Consumer loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans
PCI Loans [Member] | Other consumer [Member] | Consumer loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	$ 226	$ 314