Loans and Allowance for Loan Losses - Schedule of Activity of Purchased Impaired Loans (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Financing Receivable, Impaired [Line Items]
Purchased impaired loans	$ 44,393	$ 43,526
Allowance for loan losses	(478)	(166)
Carrying amount, net of allowance	43,915	43,360
Commercial Loan [Member]
Financing Receivable, Impaired [Line Items]
Purchased impaired loans	6,193	5,152
Commercial Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Purchased impaired loans	25,391	21,826
Residential [Member]
Financing Receivable, Impaired [Line Items]
Purchased impaired loans	9,257	11,303
Consumer Loan [Member]
Financing Receivable, Impaired [Line Items]
Purchased impaired loans	$ 3,552	$ 5,245

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.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 30
-Section 15
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=82894507&loc=d3e13503-111538

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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The recorded balance, net of any applicable reductions (for example, unamortized accretable yield and allowance for loan losses). This relates to loans not accounted for 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.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 30
-Section 50
-Paragraph 2
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-URI http://asc.fasb.org/extlink&oid=82894903&loc=d3e15032-111544

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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-Section 15
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-URI http://asc.fasb.org/extlink&oid=82894507&loc=d3e13503-111538

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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.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 30
-Section 15
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=82894507&loc=d3e13503-111538

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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