Loans - Risk Category of Loans (Detail) (Non-PCI Loans [Member], USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Non-PCI Loans	$ 7,344,601	$ 6,748,933
Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Non-PCI Loans	1,941,470	1,820,136
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Non-PCI Loans	4,961,990	4,521,920
Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Non-PCI Loans	441,141	406,877
Pass [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Non-PCI Loans	7,060,722	6,411,735
Pass [Member] | Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Non-PCI Loans	1,840,602	1,689,613
Pass [Member] | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Non-PCI Loans	4,803,172	4,348,642
Pass [Member] | Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Non-PCI Loans	416,948	373,480
Special Mention [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Non-PCI Loans	104,796	115,863
Special Mention [Member] | Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Non-PCI Loans	52,850	56,007
Special Mention [Member] | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Non-PCI Loans	48,623	48,159
Special Mention [Member] | Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Non-PCI Loans	3,323	11,697
Substandard [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Non-PCI Loans	173,936	215,340
Substandard [Member] | Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Non-PCI Loans	48,018	74,501
Substandard [Member] | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Non-PCI Loans	110,195	125,119
Substandard [Member] | Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Non-PCI Loans	15,723	15,720
Doubtful [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Non-PCI Loans	5,147	5,995
Doubtful [Member] | Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Non-PCI Loans		15
Doubtful [Member] | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Non-PCI Loans
Doubtful [Member] | Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Non-PCI Loans	$ 5,147	$ 5,980