Loans and the Allowance for Credit Losses - Schedule of Recorded Investment in Loans by Category (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment [Line Items]
Total portfolio loans	$ 6,792,899	$ 6,341,441
Loans held for sale	12,053	20,320
Total loans	6,804,952	6,361,761
Commercial Real Estate - Land and Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Total portfolio loans	481,690	392,597
Commercial Real Estate - Improved Property [Member]
Financing Receivable, Recorded Investment [Line Items]
Total portfolio loans	2,707,645	2,601,851
Commercial and Industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total portfolio loans	1,294,488	1,125,327
Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total portfolio loans	3,189,335	2,994,448
Residential Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total portfolio loans	1,450,829	1,353,301
Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Total portfolio loans	322,594	339,169
Home Equity [Member]
Financing Receivable, Recorded Investment [Line Items]
Total portfolio loans	$ 535,653	$ 529,196

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Amount before allowance and after deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=82891408&loc=d3e4428-111522

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5074-111524

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Fair value portion of loans held-for-sale including, but not limited to, mortgage loans and finance receivables.

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+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
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