Loans - Schedule of Loan Portfolio Non-Covered and Covered PCI Loans and Non-PCI Loans (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	$ 10,842,125	$ 9,527,797
Covered loans	180,674	271,844
Total loans	11,022,799	9,799,641
Commercial real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	4,843,153	3,985,092
Consumer loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	1,451,717	1,378,728
Covered loans	2,306	4,931
Commercial and industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	2,084,826	1,878,387
Covered loans	46,517	83,742
Commercial real estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	4,417,709	3,574,089
Covered loans	120,268	160,651
Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	425,444	411,003
Covered loans	1,924	6,974
Residential mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	2,462,429	2,285,590
Covered loans	9,659	15,546
Home equity [Member] | Consumer loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	485,458	469,604
Automobile [Member] | Consumer loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	786,528	772,490
Other consumer [Member] | Consumer loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	179,731	136,634
Non-PCI Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	9,855,135	9,527,797
Covered loans
Total loans	9,855,135	9,527,797
Non-PCI Loans [Member] | Commercial real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	4,171,939	3,985,092
Non-PCI Loans [Member] | Consumer loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	1,404,826	1,378,728
Covered loans
Non-PCI Loans [Member] | Commercial and industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	1,832,743	1,878,387
Covered loans
Non-PCI Loans [Member] | Commercial real estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	3,772,084	3,574,089
Covered loans
Non-PCI Loans [Member] | Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	399,855	411,003
Covered loans
Non-PCI Loans [Member] | Residential mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	2,445,627	2,285,590
Covered loans
Non-PCI Loans [Member] | Home equity [Member] | Consumer loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	438,881	469,604
Non-PCI Loans [Member] | Automobile [Member] | Consumer loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	786,528	772,490
Non-PCI Loans [Member] | Other consumer [Member] | Consumer loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	179,417	136,634
PCI Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	986,990
Covered loans	180,674	271,844
Total loans	1,167,664	271,844
PCI Loans [Member] | Commercial real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	671,214
PCI Loans [Member] | Consumer loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	46,891
Covered loans	2,306	4,931
PCI Loans [Member] | Commercial and industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	252,083
Covered loans	46,517	83,742
PCI Loans [Member] | Commercial real estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	645,625
Covered loans	120,268	160,651
PCI Loans [Member] | Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	25,589
Covered loans	1,924	6,974
PCI Loans [Member] | Residential mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	16,802
Covered loans	9,659	15,546
PCI Loans [Member] | Home equity [Member] | Consumer loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	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	$ 314