Loans and Allowance for Loan Losses - Schedule of Recorded Investment in Loans (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses, Individually evaluated for impairment	$ 8,897	$ 14,341
Allowance for loan losses, Collectively evaluated for impairment	45,527	40,642
Allowance for loan losses, Loans acquired with deteriorated credit quality	195	478
Total allowance for loan losses	54,619	55,461
Loans and leases outstanding, Individually evaluated for impairment	104,767	118,514
Loans and leases outstanding, Collectively evaluated for impairment	11,978,895	12,080,985
Loans and leases outstanding, Loans acquired with deteriorated credit quality	33,862	44,393
Total loans and leases outstanding	12,117,524	12,243,892
Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses, Individually evaluated for impairment	7,891	6,035
Allowance for loan losses, Collectively evaluated for impairment	14,692	15,700
Allowance for loan losses, Loans acquired with deteriorated credit quality	2	7
Total allowance for loan losses	22,585	21,742
Loans and leases outstanding, Individually evaluated for impairment	41,479	35,410
Loans and leases outstanding, Collectively evaluated for impairment	2,843,536	3,191,367
Loans and leases outstanding, Loans acquired with deteriorated credit quality	5,281	6,193
Total loans and leases outstanding	2,890,296	3,232,970
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses, Individually evaluated for impairment	1,006	8,306
Allowance for loan losses, Collectively evaluated for impairment	20,582	14,845
Allowance for loan losses, Loans acquired with deteriorated credit quality		319
Total allowance for loan losses	21,588	23,470
Loans and leases outstanding, Individually evaluated for impairment	63,288	83,104
Loans and leases outstanding, Collectively evaluated for impairment	5,084,737	4,850,356
Loans and leases outstanding, Loans acquired with deteriorated credit quality	18,767	25,391
Total loans and leases outstanding	5,166,792	4,958,851
Residential [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses, Collectively evaluated for impairment	2,299	2,276
Allowance for loan losses, Loans acquired with deteriorated credit quality		1
Total allowance for loan losses	2,299	2,277
Loans and leases outstanding, Collectively evaluated for impairment	2,326,907	2,239,147
Loans and leases outstanding, Loans acquired with deteriorated credit quality	7,382	9,257
Total loans and leases outstanding	2,334,289	2,248,404
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses, Collectively evaluated for impairment	7,954	7,821
Allowance for loan losses, Loans acquired with deteriorated credit quality	193	151
Total allowance for loan losses	8,147	7,972
Loans and leases outstanding, Collectively evaluated for impairment	1,723,715	1,800,115
Loans and leases outstanding, Loans acquired with deteriorated credit quality	2,432	3,552
Total loans and leases outstanding	$ 1,726,147	$ 1,803,667

Reserve for loans impairments recorded after acquisition as a result of current information and events which result in it being probable that estimated cash flows will be less than previously expected or because actual cash flows are less than cash flows previously expected. This relates to loans not accounted for as debt securities, with evidence of deterioration of credit quality since origination that was acquired by completion of a transfer for which it is probable, at acquisition, that the investor will be unable to collect all contractually required payments receivable.

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The undiscounted sum of all amounts, including amounts deemed principal, interest, fees, penalties, and other under the loan, owed to the investor at the reporting date, whether or not currently due and whether or not any such amounts have been written or charged off by the investor. This relates to loans not accounted for as debt securities, with evidence of deterioration of credit quality since origination that were acquired by completion of a transfer for which it is probable, at acquisition, that the investor will be unable to collect all contractually required payments receivable.

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Amount of allowance for credit loss on financing receivable. Excludes allowance for financing receivable covered under loss sharing agreement.

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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.

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