Loans and Allowance for Loan Losses - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	$ 9,943,136		$ 9,506,094
Outstanding contractual balance receivable of acquired loans	1,704,889		1,449,227
Commercial construction loans	270,913		252,842
Payoffs received on loans in excess of expected cash flows	242		440
Threshold period past due for default status of trade accounts receivable	90 days	90 days
Minimum corporation reserves for commercial loan	500
Minimum amount to allocate specific valuation allowance	500
Recorded Investment	9,525
Allowance for loan losses	5,096		5,900
Restructured loans returned to performing status	3,194
Specific reserves in allowance for loan losses, TDRs	523		561
Pooled reserves in allowance for loan losses, TDRs	188		193
Valuation for impairment of loans with pooled reserves	500		500
Pooled reserves for all other classes of loans	1,026		1,005
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	3,464,598		3,245,209
Recorded Investment	46,331		44,075
Allowance for loan losses	2,612		3,093
Commercial Real Estate [Member] | FLORIDA [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial real estate loans	39,118		39,379
Percentage of loan portfolio	0.40%		0.40%
Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	1,965,065		1,881,474
Recorded Investment	5,153		7,423
Allowance for loan losses	817		786
Direct Installment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	1,467,558		1,467,236
Recorded Investment	12,047		10,577
Allowance for loan losses	906		727
Residential Mortgages [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	1,135,790		1,086,739
Recorded Investment	13,961		14,012
Allowance for loan losses	504		970
Indirect Installment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	678,918		655,587
Recorded Investment	1,399		1,202
Allowance for loan losses	257		324
Consumer Lines of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	1,010,501		965,771
Percentage of loan portfolio	1.70%		1.90%
Consumer loans	171,228		179,970
Recorded Investment	922		597
Commercial Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of loan portfolio	2.70%		2.70%
Acquired Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	1,593,642		1,345,429
Purchased Credit-Impaired Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Carrying Amount	14,513		21,192
Outstanding contractual receivable of PCI loan	46,809		56,500
Recorded Investment	$ 15,221		$ 22,192
Owner-Occupied [Member] | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of loan portfolio	42.00%		43.10%
Non-Owner-Occupied [Member] | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of loan portfolio	58.00%		56.90%
Commercial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Threshold period past due for default non-accrual status of trade accounts receivable	90 days
Installment Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Threshold period past due for default non-accrual status of trade accounts receivable	120 days
Residential Mortgages [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Threshold period past due for default non-accrual status of trade accounts receivable	180 days