Loans and Allowance for Loan Losses - Summary of Changes in Allowance for Loan Losses by Class (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Schedule Of Allowance For Loan Losses [Line Items]
Balance at Beginning of Year	$ 110,784	$ 104,374
Charge- Offs	(7,103)	(6,804)
Recoveries	1,532	2,591
Net Charge- Offs	(5,571)	(4,213)
Provision for loan losses	7,006	7,541
Balance at End of Year	112,219	107,702
Originated Loans [Member]
Schedule Of Allowance For Loan Losses [Line Items]
Balance at Beginning of Year	104,884	100,194
Charge- Offs	(6,863)	(6,435)
Recoveries	1,246	2,387
Net Charge- Offs	(5,617)	(4,048)
Provision for loan losses	7,856	6,358
Balance at End of Year	107,123	102,504
Acquired Loans [Member]
Schedule Of Allowance For Loan Losses [Line Items]
Balance at Beginning of Year	5,900	4,180
Charge- Offs	(240)	(369)
Recoveries	286	204
Net Charge- Offs	46	(165)
Provision for loan losses	(850)	1,183
Balance at End of Year	5,096	5,198
Commercial Real Estate [Member]
Schedule Of Allowance For Loan Losses [Line Items]
Balance at Beginning of Year	32,548	34,810
Charge- Offs	(2,223)	(2,287)
Recoveries	299	1,427
Net Charge- Offs	(1,924)	(860)
Provision for loan losses	7,910	6,062
Balance at End of Year	38,534	40,012
Commercial and Industrial [Member]
Schedule Of Allowance For Loan Losses [Line Items]
Balance at Beginning of Year	32,603	31,849
Charge- Offs	(513)	(208)
Recoveries	370	356
Net Charge- Offs	(143)	148
Provision for loan losses	(2,489)	(3,159)
Balance at End of Year	29,971	28,838
Commercial Leases [Member]
Schedule Of Allowance For Loan Losses [Line Items]
Balance at Beginning of Year	1,903	1,744
Charge- Offs	(87)	(57)
Recoveries	29	62
Net Charge- Offs	(58)	5
Provision for loan losses	99	(53)
Balance at End of Year	1,944	1,696
Total Commercial Loans and Leases [Member]
Schedule Of Allowance For Loan Losses [Line Items]
Balance at Beginning of Year	67,054	68,403
Charge- Offs	(2,823)	(2,552)
Recoveries	698	1,845
Net Charge- Offs	(2,125)	(707)
Provision for loan losses	5,520	2,850
Balance at End of Year	70,449	70,546
Direct Installment [Member]
Schedule Of Allowance For Loan Losses [Line Items]
Balance at Beginning of Year	17,824	15,130
Charge- Offs	(2,521)	(2,345)
Recoveries	267	233
Net Charge- Offs	(2,254)	(2,112)
Provision for loan losses	1,060	2,082
Balance at End of Year	16,630	15,100
Residential Mortgages [Member]
Schedule Of Allowance For Loan Losses [Line Items]
Balance at Beginning of Year	5,836	5,155
Charge- Offs	(132)	(209)
Recoveries	4	29
Net Charge- Offs	(128)	(180)
Provision for loan losses	(401)	3
Balance at End of Year	5,307	4,978
Indirect Installment [Member]
Schedule Of Allowance For Loan Losses [Line Items]
Balance at Beginning of Year	6,409	5,449
Charge- Offs	(802)	(810)
Recoveries	217	193
Net Charge- Offs	(585)	(617)
Provision for loan losses	676	320
Balance at End of Year	6,500	5,152
Consumer Lines of Credit [Member]
Schedule Of Allowance For Loan Losses [Line Items]
Balance at Beginning of Year	7,231	6,057
Charge- Offs	(323)	(342)
Recoveries	55	87
Net Charge- Offs	(268)	(255)
Provision for loan losses	695	243
Balance at End of Year	7,658	6,045
Other [Member]
Schedule Of Allowance For Loan Losses [Line Items]
Balance at Beginning of Year	530
Charge- Offs	(262)	(177)
Recoveries	5
Net Charge- Offs	(257)	(177)
Provision for loan losses	306	860
Balance at End of Year	579	683
Purchased Credit-Impaired Loans [Member]
Schedule Of Allowance For Loan Losses [Line Items]
Balance at Beginning of Year	1,000	759
Charge- Offs	(249)	(156)
Recoveries
Net Charge- Offs	(249)	(156)
Provision for loan losses	(43)	(20)
Balance at End of Year	708	583
Other Acquired Loans [Member]
Schedule Of Allowance For Loan Losses [Line Items]
Balance at Beginning of Year	4,900	3,421
Charge- Offs	9	(213)
Recoveries	286	204
Net Charge- Offs	295	(9)
Provision for loan losses	(807)	1,203
Balance at End of Year	$ 4,388	$ 4,615