Loans and Leases (Loans and Leases, Net of Deferred Costs and Fees) (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
Loans And Leases Receivable Net Of Deferred Costs And Fees By Type [Line Items]
Total loans and leases	$ 13,300,309,000	$ 12,728,082,000
Nonaccrual loans and leases	101,976,000	97,767,000
Loans and leases contractually past due 90 days and still accruing	8,655,000	8,209,000
Troubled Debt Restructurings	69,975,000	67,775,000
Deferred origination costs and fees	20,278,000	17,763,000
All overdrawn deposit accounts, reclassified as loans and evaluated for collectability	2,550,000	15,422,000
Commercial, Financial, And Agricultural [Member]
Loans And Leases Receivable Net Of Deferred Costs And Fees By Type [Line Items]
Total loans and leases	2,273,735,000	2,273,611,000
Real Estate - Construction [Member]
Loans And Leases Receivable Net Of Deferred Costs And Fees By Type [Line Items]
Total loans and leases	765,246,000	847,781,000
Real Estate Secured - Residential [Member]
Loans And Leases Receivable Net Of Deferred Costs And Fees By Type [Line Items]
Total loans and leases	4,145,522,000	4,065,818,000
Real Estate Secured - Commercial [Member]
Loans And Leases Receivable Net Of Deferred Costs And Fees By Type [Line Items]
Total loans and leases	4,109,329,000	3,964,608,000
Consumer [Member]
Loans And Leases Receivable Net Of Deferred Costs And Fees By Type [Line Items]
Total loans and leases	935,117,000	842,552,000
Leases [Member]
Loans And Leases Receivable Net Of Deferred Costs And Fees By Type [Line Items]
Total loans and leases	1,147,505,000	900,371,000
Total Loans And Leases [Member]
Loans And Leases Receivable Net Of Deferred Costs And Fees By Type [Line Items]
Total loans and leases	13,376,454,000	12,894,741,000
Originated Loans And Leases [Member]
Loans And Leases Receivable Net Of Deferred Costs And Fees By Type [Line Items]
Total loans and leases	11,622,463,000	10,765,458,000
Purchased Loans And Leases [Member]
Loans And Leases Receivable Net Of Deferred Costs And Fees By Type [Line Items]
Total loans and leases	$ 1,753,991,000	$ 2,129,283,000