Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

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- Definition

Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

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- Definition

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.

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Amount after allowance and 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 and loans held for sale.

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Loans and Allowance for Loan Losses - Schedule of Composition of Loan (Detail) (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans by lending classification	$ 12,068,977	$ 12,243,892	$ 11,238,682
Allowance for loan losses	(55,559)	(55,461)	(50,381)	$ (50,381)
Net loans	12,013,418	12,188,431	11,188,301
Commercial Loan [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans by lending classification	3,042,790	3,232,970
Allowance for loan losses	(20,406)	(21,742)	$ (19,591)	$ (19,246)
Residential Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans by lending classification	2,243,885	2,248,404
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans by lending classification	5,023,620	4,958,851
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans by lending classification	1,758,682	1,803,667
Consumer [Member] \| Consumer Credit - Home Equity [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans by lending classification	553,264	589,322
Construction [Member] \| Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans by lending classification	552,825	504,625
Other [Member] \| Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans by lending classification	4,470,795	4,454,226
Other [Member] \| Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans by lending classification	171,071	154,712
Consumer Credit - Auto [Member] \| Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans by lending classification	$ 1,034,347	$ 1,059,633