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		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Balance at Beginning of Period	$ 108,280	$ 101,647	$ 104,374	$ 100,662
Charge- Offs	(5,844)	(9,220)	(20,811)	(23,563)
Recoveries	336	1,858	3,765	3,587
Net Charge- Offs	(5,508)	(7,362)	(17,046)	(19,976)
Provision for loan losses	7,280	8,429	22,724	22,028
Balance at End of Period	110,052	102,714	110,052	102,714
Commercial Real Estate [Member]
Balance at Beginning of Period	35,666	38,480	34,810	43,283
Charge- Offs	(365)	(1,481)	(3,067)	(4,733)
Recoveries	80	1,375	1,606	1,634
Net Charge- Offs	(285)	(106)	(1,461)	(3,099)
Provision for loan losses	(538)	(3,360)	1,494	(5,170)
Balance at End of Period	34,843	35,014	34,843	35,014
Commercial and Industrial [Member]
Balance at Beginning of Period	32,486	30,779	31,849	25,476
Charge- Offs	(1,529)	(3,746)	(4,262)	(7,086)
Recoveries	231	(19)	734	349
Net Charge- Offs	(1,298)	(3,765)	(3,528)	(6,737)
Provision for loan losses	1,460	4,861	4,327	13,136
Balance at End of Period	32,648	31,875	32,648	31,875
Commercial Leases [Member]
Balance at Beginning of Period	1,756	1,674	1,744	1,556
Charge- Offs	(69)	(216)	(317)	(509)
Recoveries	59	78	161	177
Net Charge- Offs	(10)	(138)	(156)	(332)
Provision for loan losses	21	214	179	526
Balance at End of Period	1,767	1,750	1,767	1,750
Commercial Loans [Member]
Balance at Beginning of Period	69,908	70,933	68,403	70,315
Charge- Offs	(1,963)	(5,443)	(7,646)	(12,328)
Recoveries	370	1,434	2,501	2,160
Net Charge- Offs	(1,593)	(4,009)	(5,145)	(10,168)
Provision for loan losses	943	1,715	6,000	8,492
Balance at End of Period	69,258	68,639	69,258	68,639
Direct Installment [Member]
Balance at Beginning of Period	15,993	14,536	15,130	14,814
Charge- Offs	(2,183)	(1,985)	(6,824)	(5,908)
Recoveries	227	225	709	721
Net Charge- Offs	(1,956)	(1,760)	(6,115)	(5,187)
Provision for loan losses	3,194	1,929	8,216	5,078
Balance at End of Period	17,231	14,705	17,231	14,705
Residential Mortgages [Member]
Balance at Beginning of Period	5,120	4,259	5,155	4,437
Charge- Offs	(174)	(3)	(733)	(644)
Recoveries	50	4	90	127
Net Charge- Offs	(124)	1	(643)	(517)
Provision for loan losses	437	256	921	596
Balance at End of Period	5,433	4,516	5,433	4,516
Indirect Installment [Member]
Balance at Beginning of Period	5,626	5,666	5,449	5,503
Charge- Offs	(807)	(688)	(2,349)	(2,128)
Recoveries	188	158	576	433
Net Charge- Offs	(619)	(530)	(1,773)	(1,695)
Provision for loan losses	1,120	539	2,451	1,867
Balance at End of Period	6,127	5,675	6,127	5,675
Consumer Lines of Credit [Member]
Balance at Beginning of Period	6,421	5,266	6,057	5,447
Charge- Offs	(454)	(831)	(1,183)	(1,585)
Recoveries	60	37	209	146
Net Charge- Offs	(394)	(794)	(974)	(1,439)
Provision for loan losses	1,052	1,556	1,996	2,020
Balance at End of Period	7,079	6,028	7,079	6,028
Other [Member]
Balance at Beginning of Period	(219)	203		146
Charge- Offs	(333)	(270)	(721)	(716)
Recoveries
Net Charge- Offs	(333)	(270)	(721)	(716)
Provision for loan losses	760	229	929	732
Balance at End of Period	208	162	208	162
Originated Loans [Member]
Balance at Beginning of Period	102,849	100,863	100,194	100,662
Charge- Offs	(5,914)	(9,220)	(19,456)	(23,309)
Recoveries	895	1,858	4,085	3,587
Net Charge- Offs	(5,019)	(7,362)	(15,371)	(19,722)
Provision for loan losses	7,506	6,224	20,513	18,785
Balance at End of Period	105,336	99,725	105,336	99,725
Purchased Credit-Impaired Loans [Member]
Balance at Beginning of Period	325	784	759
Charge- Offs			(156)	(254)
Recoveries
Net Charge- Offs			(156)	(254)
Provision for loan losses	337	2,205	59	3,243
Balance at End of Period	662	2,989	662	2,989
Other Acquired Loans [Member]
Balance at Beginning of Period	5,106		3,421
Charge- Offs	70		(1,199)
Recoveries	(559)		(320)
Net Charge- Offs	(489)		(1,519)
Provision for loan losses	(563)		2,152
Balance at End of Period	4,054		4,054
Acquired Loans [Member]
Balance at Beginning of Period	5,431	784	4,180
Charge- Offs	70		(1,355)	(254)
Recoveries	(559)		(320)
Net Charge- Offs	(489)		(1,675)	(254)
Provision for loan losses	(226)	2,205	2,211	3,243
Balance at End of Period	$ 4,716	$ 2,989	$ 4,716	$ 2,989