Allowance for Credit Losses - Summary of Changes in Allowance for Credit Losses by Loan and Lease Class (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Schedule Of Allowance For Loan Losses [Line Items]
Balance at Beginning of Period	$ 147,800	$ 128,499	$ 142,012	$ 125,926
Charge- Offs	(12,914)	(8,188)	(20,798)	(15,076)
Recoveries	2,843	1,966	4,747	3,291
Net Charge- Offs	(10,071)	(6,222)	(16,051)	(11,785)
Provision for credit losses	16,640	8,864	28,408	17,000
Balance at End of Period	154,369	131,141	154,369	131,141
Originated Loans and Leases [Member]
Schedule Of Allowance For Loan Losses [Line Items]
Balance at Beginning of Period	142,220	121,247	135,285	117,952
Charge- Offs	(12,449)	(7,720)	(19,952)	(14,467)
Recoveries	2,564	1,925	4,162	2,901
Net Charge- Offs	(9,885)	(5,795)	(15,790)	(11,566)
Provision for credit losses	16,384	8,744	29,224	17,810
Balance at End of Period	148,719	124,196	148,719	124,196
Acquired Loans [Member]
Schedule Of Allowance For Loan Losses [Line Items]
Balance at Beginning of Period	5,580	7,252	6,727	7,974
Charge- Offs	(465)	(468)	(846)	(609)
Recoveries	279	41	585	390
Net Charge- Offs	(186)	(427)	(261)	(219)
Provision for credit losses	256	120	(816)	(810)
Balance at End of Period	5,650	6,945	5,650	6,945
Commercial Real Estate [Member]
Schedule Of Allowance For Loan Losses [Line Items]
Balance at Beginning of Period	43,898	38,792	41,741	37,588
Charge- Offs	(666)	(977)	(2,035)	(1,978)
Recoveries	1,109	200	1,706	409
Net Charge- Offs	443	(777)	(329)	(1,569)
Provision for credit losses	87	1,857	3,016	3,853
Balance at End of Period	44,428	39,872	44,428	39,872
Commercial and Industrial [Member]
Schedule Of Allowance For Loan Losses [Line Items]
Balance at Beginning of Period	47,863	32,803	41,023	32,645
Charge- Offs	(5,671)	(1,416)	(5,969)	(2,100)
Recoveries	190	976	380	1,096
Net Charge- Offs	(5,481)	(440)	(5,589)	(1,004)
Provision for credit losses	9,093	(58)	16,041	664
Balance at End of Period	51,475	32,305	51,475	32,305
Commercial Leases [Member]
Schedule Of Allowance For Loan Losses [Line Items]
Balance at Beginning of Period	2,818	2,576	2,541	2,398
Charge- Offs	(603)	(111)	(717)	(204)
Recoveries	32	35	46	45
Net Charge- Offs	(571)	(76)	(671)	(159)
Provision for credit losses	800	(277)	1,177	(16)
Balance at End of Period	3,047	2,223	3,047	2,223
Total Commercial Loans and Leases [Member]
Schedule Of Allowance For Loan Losses [Line Items]
Balance at Beginning of Period	94,579	74,171	85,305	72,631
Charge- Offs	(6,940)	(2,504)	(8,721)	(4,282)
Recoveries	1,331	1,211	2,132	1,550
Net Charge- Offs	(5,609)	(1,293)	(6,589)	(2,732)
Provision for credit losses	9,980	1,522	20,234	4,501
Balance at End of Period	98,950	74,400	98,950	74,400
Direct Installment [Member]
Schedule Of Allowance For Loan Losses [Line Items]
Balance at Beginning of Period	20,725	21,204	21,587	20,538
Charge- Offs	(2,421)	(2,953)	(5,088)	(5,386)
Recoveries	454	297	908	566
Net Charge- Offs	(1,967)	(2,656)	(4,180)	(4,820)
Provision for credit losses	2,785	3,731	4,136	6,561
Balance at End of Period	21,543	22,279	21,543	22,279
Residential Mortgages [Member]
Schedule Of Allowance For Loan Losses [Line Items]
Balance at Beginning of Period	7,810	8,471	7,909	8,024
Charge- Offs	(72)	(112)	(157)	(623)
Recoveries	38	24	57	39
Net Charge- Offs	(34)	(88)	(100)	(584)
Provision for credit losses	634	196	601	1,139
Balance at End of Period	8,410	8,579	8,410	8,579
Indirect Installment [Member]
Schedule Of Allowance For Loan Losses [Line Items]
Balance at Beginning of Period	9,065	7,657	9,889	7,504
Charge- Offs	(1,763)	(1,503)	(3,705)	(2,783)
Recoveries	666	332	928	634
Net Charge- Offs	(1,097)	(1,171)	(2,777)	(2,149)
Provision for credit losses	1,575	2,423	2,431	3,554
Balance at End of Period	9,543	8,909	9,543	8,909
Consumer Lines of Credit [Member]
Schedule Of Allowance For Loan Losses [Line Items]
Balance at Beginning of Period	8,967	8,890	9,582	8,496
Charge- Offs	(528)	(323)	(1,002)	(733)
Recoveries	49	36	105	76
Net Charge- Offs	(479)	(287)	(897)	(657)
Provision for credit losses	661	515	464	1,279
Balance at End of Period	9,149	9,118	9,149	9,118
Other [Member]
Schedule Of Allowance For Loan Losses [Line Items]
Balance at Beginning of Period	1,074	854	1,013	759
Charge- Offs	(725)	(325)	(1,279)	(660)
Recoveries	26	25	32	36
Net Charge- Offs	(699)	(300)	(1,247)	(624)
Provision for credit losses	749	357	1,358	776
Balance at End of Period	1,124	911	1,124	911
Purchased Credit-Impaired Loans [Member]
Schedule Of Allowance For Loan Losses [Line Items]
Balance at Beginning of Period	704	621	834	660
Charge- Offs	(239)		(399)	(64)
Recoveries				19
Net Charge- Offs	(239)		(399)	(45)
Provision for credit losses	167	37	197	43
Balance at End of Period	632	658	632	658
Other Acquired Loans [Member]
Schedule Of Allowance For Loan Losses [Line Items]
Balance at Beginning of Period	4,876	6,631	5,893	7,314
Charge- Offs	(226)	(468)	(447)	(545)
Recoveries	279	41	585	371
Net Charge- Offs	53	(427)	138	(174)
Provision for credit losses	89	83	(1,013)	(853)
Balance at End of Period	$ 5,018	$ 6,287	$ 5,018	$ 6,287