Loans and Leases (Loans and Leases, Net of Deferred Costs and Fees) (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Loans And Leases Receivable Net Of Deferred Costs And Fees By Type [Line Items]
Total loans and leases	$ 13,157,762	$ 12,894,741
Nonaccrual loans and leases	105,110	97,767
Loans and leases contractually past due 90 days and still accruing	7,203	8,209
Troubled Debt Restructurings	63,822	67,775
Deferred origination costs and fees	18,756	17,763
All overdrawn deposit accounts, reclassified as loans and evaluated for collectability	2,068	15,422
Commercial, Financial, And Agricultural [Member]
Loans And Leases Receivable Net Of Deferred Costs And Fees By Type [Line Items]
Total loans and leases	2,289,159	2,273,611
Real Estate - Construction [Member]
Loans And Leases Receivable Net Of Deferred Costs And Fees By Type [Line Items]
Total loans and leases	769,722	847,781
Real Estate Secured - Residential [Member]
Loans And Leases Receivable Net Of Deferred Costs And Fees By Type [Line Items]
Total loans and leases	4,098,938	4,065,818
Real Estate Secured - Commercial [Member]
Loans And Leases Receivable Net Of Deferred Costs And Fees By Type [Line Items]
Total loans and leases	4,029,454	3,964,608
Consumer [Member]
Loans And Leases Receivable Net Of Deferred Costs And Fees By Type [Line Items]
Total loans and leases	908,328	842,552
Leases [Member]
Loans And Leases Receivable Net Of Deferred Costs And Fees By Type [Line Items]
Total loans and leases	1,062,161	900,371
Originated Loans And Leases [Member]
Loans And Leases Receivable Net Of Deferred Costs And Fees By Type [Line Items]
Total loans and leases	11,300,821	10,765,458
Purchased Loans And Leases [Member]
Loans And Leases Receivable Net Of Deferred Costs And Fees By Type [Line Items]
Total loans and leases	$ 1,856,941	$ 2,129,283