Loans - Risk Category of Loans (Detail) (Non-PCI Loans [Member], USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 6,004,682	$ 5,863,479
Commercial and industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	1,832,743	1,878,387
Commercial real estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	3,772,084	3,574,089
Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	399,855	411,003
Pass [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	5,577,491	5,350,266
Pass [Member] | Commercial and industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	1,673,604	1,669,943
Pass [Member] | Commercial real estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	3,563,530	3,350,475
Pass [Member] | Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	340,357	329,848
Special Mention [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	156,769	221,183
Special Mention [Member] | Commercial and industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	64,777	95,726
Special Mention [Member] | Commercial real estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	59,175	82,612
Special Mention [Member] | Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	32,817	42,845
Substandard [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	263,084	291,302
Substandard [Member] | Commercial and industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	94,184	112,186
Substandard [Member] | Commercial real estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	149,379	141,002
Substandard [Member] | Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	19,521	38,114
Doubtful [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	7,338	728
Doubtful [Member] | Commercial and industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	178	532
Doubtful [Member] | Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 7,160	$ 196