Loans - Schedule of Loan Portfolio Non-Covered and Covered PCI Loans and Non-PCI Loans (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	$ 11,750,875	$ 11,471,447
Covered loans	62,553	96,165
Total loans	11,813,428	11,567,612
Commercial Real Estate Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	5,513,704	5,410,906
Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	1,710,904	1,565,492
Covered loans	506	799
Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	2,064,751	1,995,084
Covered loans	15,861	26,249
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	5,100,442	4,981,675
Covered loans	38,738	61,494
Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	413,262	429,231
Residential Mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	2,461,516	2,499,965
Covered loans	7,448	7,623
Home Equity [Member] | Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	436,360	449,009
Automobile [Member] | Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	1,021,782	901,399
Other Consumer [Member] | Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	252,762	215,084
Non-PCI Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	11,137,823	10,761,344
Covered loans	0
Total loans	11,137,823	10,761,344
Non-PCI Loans [Member] | Commercial Real Estate Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	5,104,171	4,928,797
Non-PCI Loans [Member] | Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	1,674,688	1,527,172
Covered loans
Non-PCI Loans [Member] | Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	1,910,990	1,820,136
Covered loans
Non-PCI Loans [Member] | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	4,707,209	4,521,920
Covered loans
Non-PCI Loans [Member] | Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	396,962	406,877
Non-PCI Loans [Member] | Residential Mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	2,447,974	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	400,303	410,875
Non-PCI Loans [Member] | Automobile [Member] | Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	1,021,782	901,399
Non-PCI Loans [Member] | Other Consumer [Member] | Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	252,603	214,898
PCI Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	613,052	710,103
Covered loans	62,553	96,165
Total loans	675,605	806,268
PCI Loans [Member] | Commercial Real Estate Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	409,533	482,109
PCI Loans [Member] | Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	36,216	38,320
Covered loans	506	799
PCI Loans [Member] | Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	153,761	174,948
Covered loans	15,861	26,249
PCI Loans [Member] | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	393,233	459,755
Covered loans	38,738	61,494
PCI Loans [Member] | Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	16,300	22,354
PCI Loans [Member] | Residential Mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	13,542	14,726
Covered loans	7,448	7,623
PCI Loans [Member] | Home Equity [Member] | Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	36,057	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	$ 159	$ 186