Loans (Loans) (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial and industrial	$ 4,828,612	$ 3,916,867
Commercial mortgages	2,495,481	2,383,479
Construction	608,306	434,870
Land	216,008	202,478
Commercial real estate	3,319,795	3,020,827
Home equity loans	310,675	282,244
Home equity lines of credit	186,522	191,960
1-4 family residential mortgages	38,323	45,943
Construction	17,621	17,544
Other	224,206	225,118
Total consumer real estate	777,347	762,809
Total real estate	4,097,142	3,783,636
Consumer installment	311,310	301,518
Other	8,435	11,018
Total consumer and other	319,745	312,536
Unearned discounts	(21,651)	(17,910)
Total Loans	9,223,848	7,995,129
Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial and industrial	4,357,100	3,553,989
Leases [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial and industrial	278,535	193,412
Asset-Based [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial and industrial	$ 192,977	$ 169,466