Loans and Leases (Loans and Leases, Net of Deferred Costs and Fees) (Detail) (USD $)	Jun. 30, 2014	Dec. 31, 2013
Loans And Leases Receivable Net Of Deferred Costs And Fees By Type [Line Items]
Total loans and leases	$ 13,600,254,000	$ 13,503,392,000
Nonaccrual loans and leases	105,609,000	100,815,000
Loans and leases contractually past due 90 days and still accruing	9,190,000	9,757,000
Troubled Debt Restructurings	40,938,000	72,133,000
Deferred origination costs, net of fees	24,441,000	21,216,000
All overdrawn deposit accounts, reclassified as loans and evaluated for collectability	6,477,000	2,918,000
Commercial, Financial, And Agricultural [Member]
Loans And Leases Receivable Net Of Deferred Costs And Fees By Type [Line Items]
Total loans and leases	2,422,931,000	2,394,847,000
Real Estate - Construction [Member]
Loans And Leases Receivable Net Of Deferred Costs And Fees By Type [Line Items]
Total loans and leases	748,181,000	735,877,000
Real Estate Secured - Residential [Member]
Loans And Leases Receivable Net Of Deferred Costs And Fees By Type [Line Items]
Total loans and leases	4,178,842,000	4,204,430,000
Real Estate Secured - Commercial [Member]
Loans And Leases Receivable Net Of Deferred Costs And Fees By Type [Line Items]
Total loans and leases	4,053,990,000	4,068,816,000
Consumer [Member]
Loans And Leases Receivable Net Of Deferred Costs And Fees By Type [Line Items]
Total loans and leases	962,618,000	953,000,000
Leases [Member]
Loans And Leases Receivable Net Of Deferred Costs And Fees By Type [Line Items]
Total loans and leases	1,300,591,000	1,219,116,000
Total Loans And Leases [Member]
Loans And Leases Receivable Net Of Deferred Costs And Fees By Type [Line Items]
Total loans and leases	13,667,153,000	13,576,086,000
Originated Loans And Leases [Member]
Loans And Leases Receivable Net Of Deferred Costs And Fees By Type [Line Items]
Total loans and leases	12,159,274,000	11,930,946,000
Purchased Loans And Leases [Member]
Loans And Leases Receivable Net Of Deferred Costs And Fees By Type [Line Items]
Total loans and leases	$ 1,507,879,000	$ 1,645,140,000