Loans and Leases (Loans and Leases, Net of Deferred Costs and Fees) (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Loans And Leases Receivable Net Of Deferred Costs And Fees By Type [Line Items]
Total loans and leases	$ 12,999,703	$ 12,894,741
Nonaccrual loans and leases	103,351	97,767
Loans and leases contractually past due 90 days and still accruing	6,396	8,209
Troubled Debt Restructurings	65,773	67,775
Deferred origination costs and fees	18,149	17,763
All overdrawn deposit accounts, reclassified as loans and evaluated for collectability	2,375	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	2,312,660	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	779,344	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	4,077,810	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	3,971,438	3,964,608
Consumer [Member]
Loans And Leases Receivable Net Of Deferred Costs And Fees By Type [Line Items]
Total loans and leases	859,664	842,552
Leases [Member]
Loans And Leases Receivable Net Of Deferred Costs And Fees By Type [Line Items]
Total loans and leases	998,787	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	10,998,299	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	$ 2,001,404	$ 2,129,283