Allowance for Credit Losses - Summary of Changes in Allowance for Credit Losses by Loan and Lease Class (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Schedule Of Allowance For Loan Losses [Line Items]
Balance at Beginning of Period	$ 154,369	$ 131,141	$ 142,012	$ 125,926
Charge- Offs	(16,187)	(7,634)	(36,985)	(22,710)
Recoveries	4,073	1,899	8,820	5,190
Net Charge- Offs	(12,114)	(5,735)	(28,165)	(17,520)
Provision for credit losses	14,639	10,777	43,047	27,777
Balance at End of Period	156,894	136,183	156,894	136,183
Originated Loans and Leases [Member]
Schedule Of Allowance For Loan Losses [Line Items]
Balance at Beginning of Period	148,719	124,196	135,285	117,952
Charge- Offs	(15,947)	(7,481)	(35,899)	(21,948)
Recoveries	3,669	1,617	7,831	4,518
Net Charge- Offs	(12,278)	(5,864)	(28,068)	(17,430)
Provision for credit losses	14,072	11,287	43,296	29,097
Balance at End of Period	150,513	129,619	150,513	129,619
Acquired Loans [Member]
Schedule Of Allowance For Loan Losses [Line Items]
Balance at Beginning of Period	5,650	6,945	6,727	7,974
Charge- Offs	(240)	(153)	(1,086)	(762)
Recoveries	404	282	989	672
Net Charge- Offs	164	129	(97)	(90)
Provision for credit losses	567	(510)	(249)	(1,320)
Balance at End of Period	6,381	6,564	6,381	6,564
Commercial Real Estate [Member]
Schedule Of Allowance For Loan Losses [Line Items]
Balance at Beginning of Period	44,428	39,872	41,741	37,588
Charge- Offs	(3,537)	(1,259)	(5,572)	(3,237)
Recoveries	1,810	370	3,516	779
Net Charge- Offs	(1,727)	(889)	(2,056)	(2,458)
Provision for credit losses	(334)	2,870	2,682	6,723
Balance at End of Period	42,367	41,853	42,367	41,853
Commercial and Industrial [Member]
Schedule Of Allowance For Loan Losses [Line Items]
Balance at Beginning of Period	51,475	32,305	41,023	32,645
Charge- Offs	(6,753)	(584)	(12,722)	(2,684)
Recoveries	598	290	978	1,386
Net Charge- Offs	(6,155)	(294)	(11,744)	(1,298)
Provision for credit losses	8,388	3,223	24,429	3,887
Balance at End of Period	53,708	35,234	53,708	35,234
Commercial Leases [Member]
Schedule Of Allowance For Loan Losses [Line Items]
Balance at Beginning of Period	3,047	2,223	2,541	2,398
Charge- Offs	(100)	(124)	(817)	(328)
Recoveries	3	50	49	95
Net Charge- Offs	(97)	(74)	(768)	(233)
Provision for credit losses	257	265	1,434	249
Balance at End of Period	3,207	2,414	3,207	2,414
Total Commercial Loans and Leases [Member]
Schedule Of Allowance For Loan Losses [Line Items]
Balance at Beginning of Period	98,950	74,400	85,305	72,631
Charge- Offs	(10,390)	(1,967)	(19,111)	(6,249)
Recoveries	2,411	710	4,543	2,260
Net Charge- Offs	(7,979)	(1,257)	(14,568)	(3,989)
Provision for credit losses	8,311	6,358	28,545	10,859
Balance at End of Period	99,282	79,501	99,282	79,501
Direct Installment [Member]
Schedule Of Allowance For Loan Losses [Line Items]
Balance at Beginning of Period	21,543	22,279	21,587	20,538
Charge- Offs	(2,464)	(2,722)	(7,552)	(8,108)
Recoveries	545	565	1,453	1,131
Net Charge- Offs	(1,919)	(2,157)	(6,099)	(6,977)
Provision for credit losses	1,463	1,214	5,599	7,775
Balance at End of Period	21,087	21,336	21,087	21,336
Residential Mortgages [Member]
Schedule Of Allowance For Loan Losses [Line Items]
Balance at Beginning of Period	8,410	8,579	7,909	8,024
Charge- Offs	(144)	(268)	(301)	(891)
Recoveries	11	14	68	53
Net Charge- Offs	(133)	(254)	(233)	(838)
Provision for credit losses	969	341	1,570	1,480
Balance at End of Period	9,246	8,666	9,246	8,666
Indirect Installment [Member]
Schedule Of Allowance For Loan Losses [Line Items]
Balance at Beginning of Period	9,543	8,909	9,889	7,504
Charge- Offs	(1,781)	(1,650)	(5,486)	(4,433)
Recoveries	617	264	1,545	898
Net Charge- Offs	(1,164)	(1,386)	(3,941)	(3,535)
Provision for credit losses	1,983	2,090	4,414	5,644
Balance at End of Period	10,362	9,613	10,362	9,613
Consumer Lines of Credit [Member]
Schedule Of Allowance For Loan Losses [Line Items]
Balance at Beginning of Period	9,149	9,118	9,582	8,496
Charge- Offs	(459)	(472)	(1,461)	(1,205)
Recoveries	82	56	187	132
Net Charge- Offs	(377)	(416)	(1,274)	(1,073)
Provision for credit losses	499	871	963	2,150
Balance at End of Period	9,271	9,573	9,271	9,573
Other [Member]
Schedule Of Allowance For Loan Losses [Line Items]
Balance at Beginning of Period	1,124	911	1,013	759
Charge- Offs	(709)	(402)	(1,988)	(1,062)
Recoveries	3	8	35	44
Net Charge- Offs	(706)	(394)	(1,953)	(1,018)
Provision for credit losses	847	413	2,205	1,189
Balance at End of Period	1,265	930	1,265	930
Purchased Credit-Impaired Loans [Member]
Schedule Of Allowance For Loan Losses [Line Items]
Balance at Beginning of Period	632	658	834	660
Charge- Offs			(399)	(64)
Recoveries	42		42	19
Net Charge- Offs	42		(357)	(45)
Provision for credit losses	(102)	36	95	80
Balance at End of Period	572	695	572	695
Other Acquired Loans [Member]
Schedule Of Allowance For Loan Losses [Line Items]
Balance at Beginning of Period	5,018	6,287	5,893	7,314
Charge- Offs	(240)	(153)	(687)	(698)
Recoveries	362	282	947	653
Net Charge- Offs	122	129	260	(45)
Provision for credit losses	669	(546)	(344)	(1,400)
Balance at End of Period	$ 5,809	$ 5,869	$ 5,809	$ 5,869