Allowance for Credit Losses - Summary of Individual and Collective Allowance for Credit Losses and Loan and Lease Balances by Class (Detail) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Valuation Allowance [Line Items]
Originated Allowance, Individually Evaluated for Impairment	$ 6,850	$ 2,650
Originated Allowance, Collectively Evaluated for Impairment	141,869	132,635
Loans and Leases	14,563,128	12,190,440
Originated Loans and Leases Outstanding, Individually Evaluated for Impairment	37,605	23,706
Originated Loans and Leases Outstanding, Collectively Evaluated for Impairment	11,732,547	11,008,273
Commercial Real Estate [Member]
Valuation Allowance [Line Items]
Originated Allowance, Individually Evaluated for Impairment	234	321
Originated Allowance, Collectively Evaluated for Impairment	44,194	41,420
Loans and Leases	5,355,625	4,109,056
Originated Loans and Leases Outstanding, Individually Evaluated for Impairment	14,059	12,904
Originated Loans and Leases Outstanding, Collectively Evaluated for Impairment	3,774,977	3,518,242
Commercial and Industrial [Member]
Valuation Allowance [Line Items]
Originated Allowance, Individually Evaluated for Impairment	6,616	2,329
Originated Allowance, Collectively Evaluated for Impairment	44,859	38,694
Loans and Leases	3,079,605	2,601,722
Originated Loans and Leases Outstanding, Individually Evaluated for Impairment	23,546	10,802
Originated Loans and Leases Outstanding, Collectively Evaluated for Impairment	2,619,570	2,523,549
Commercial Leases [Member]
Valuation Allowance [Line Items]
Originated Allowance, Collectively Evaluated for Impairment	3,047	2,541
Loans and Leases	200,350	204,553
Originated Loans and Leases Outstanding, Collectively Evaluated for Impairment	200,350	204,553
Total Commercial Loans and Leases [Member]
Valuation Allowance [Line Items]
Originated Allowance, Individually Evaluated for Impairment	6,850	2,650
Originated Allowance, Collectively Evaluated for Impairment	92,100	82,655
Loans and Leases	8,635,580	6,915,331
Originated Loans and Leases Outstanding, Individually Evaluated for Impairment	37,605	23,706
Originated Loans and Leases Outstanding, Collectively Evaluated for Impairment	6,594,897	6,246,344
Direct Installment [Member]
Valuation Allowance [Line Items]
Originated Allowance, Collectively Evaluated for Impairment	21,543	21,587
Loans and Leases	1,830,206	1,706,636
Originated Loans and Leases Outstanding, Collectively Evaluated for Impairment	1,733,606	1,660,717
Residential Mortgages [Member]
Valuation Allowance [Line Items]
Originated Allowance, Collectively Evaluated for Impairment	8,410	7,909
Loans and Leases	1,678,646	1,395,971
Originated Loans and Leases Outstanding, Collectively Evaluated for Impairment	1,217,574	1,044,689
Indirect Installment [Member]
Valuation Allowance [Line Items]
Originated Allowance, Collectively Evaluated for Impairment	9,543	9,889
Loans and Leases	1,076,817	996,729
Originated Loans and Leases Outstanding, Collectively Evaluated for Impairment	1,076,516	996,175
Consumer Lines of Credit [Member]
Valuation Allowance [Line Items]
Originated Allowance, Collectively Evaluated for Impairment	9,149	9,582
Loans and Leases	1,290,053	1,137,255
Originated Loans and Leases Outstanding, Collectively Evaluated for Impairment	1,058,128	1,021,830
Other [Member]
Valuation Allowance [Line Items]
Originated Allowance, Collectively Evaluated for Impairment	1,124	1,013
Loans and Leases	51,826	38,518
Originated Loans and Leases Outstanding, Collectively Evaluated for Impairment	51,826	38,518
Loans and Leases [Member]
Valuation Allowance [Line Items]
Loans and Leases	11,770,152	11,031,979
Loans and Leases [Member] \| Commercial Real Estate [Member]
Valuation Allowance [Line Items]
Loans and Leases	3,789,036	3,531,146
Loans and Leases [Member] \| Commercial and Industrial [Member]
Valuation Allowance [Line Items]
Loans and Leases	2,643,116	2,534,351
Loans and Leases [Member] \| Commercial Leases [Member]
Valuation Allowance [Line Items]
Loans and Leases	200,350	204,553
Loans and Leases [Member] \| Total Commercial Loans and Leases [Member]
Valuation Allowance [Line Items]
Loans and Leases	6,632,502	6,270,050
Loans and Leases [Member] \| Direct Installment [Member]
Valuation Allowance [Line Items]
Loans and Leases	1,733,606	1,660,717
Loans and Leases [Member] \| Residential Mortgages [Member]
Valuation Allowance [Line Items]
Loans and Leases	1,217,574	1,044,689
Loans and Leases [Member] \| Indirect Installment [Member]
Valuation Allowance [Line Items]
Loans and Leases	1,076,516	996,175
Loans and Leases [Member] \| Consumer Lines of Credit [Member]
Valuation Allowance [Line Items]
Loans and Leases	1,058,128	1,021,830
Loans and Leases [Member] \| Other [Member]
Valuation Allowance [Line Items]
Loans and Leases	$ 51,826	$ 38,518

The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=66008989&loc=SL6953423-111524

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Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.

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- Definition

The balance of financing receivables that were collectively evaluated for impairment.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (h)
-URI http://asc.fasb.org/extlink&oid=66008989&loc=SL6953423-111524

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (h)
-URI http://asc.fasb.org/extlink&oid=66008989&loc=SL6953423-111524

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=65884687&loc=d3e4428-111522

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=66008989&loc=d3e5074-111524

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