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

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

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

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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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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. Includes loans held for sale. Excludes loans and leases covered under loss sharing agreements.

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Loans - Summary of Allowance for Loan and Lease Losses for Loans Evaluated Individually and Collectively for Impairment (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Jun. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Dec. 31, 2016
Loans and Leases Receivable Disclosure [Line Items]
Individually evaluated for impairment	$ 2,260		$ 4,417
Collectively evaluated for impairment	370,440		329,293
Total loans	372,700		333,710
Individually evaluated for impairment	12		230
Collectively evaluated for impairment	3,230		2,863
Total allowance for loan and lease losses	3,242	$ 3,092	3,093	$ 3,069	$ 3,048	$ 3,008
Commercial [Member]
Loans and Leases Receivable Disclosure [Line Items]
Individually evaluated for impairment	938		2,529
Collectively evaluated for impairment	219,030		176,864
Total loans	219,968		179,393
Collectively evaluated for impairment	1,429		1,368
Total allowance for loan and lease losses	1,429	1,380	1,368	1,360	1,355	1,344
Residential [Member]
Loans and Leases Receivable Disclosure [Line Items]
Individually evaluated for impairment	1,322		1,888
Collectively evaluated for impairment	111,524		107,590
Total loans	112,846		109,478
Individually evaluated for impairment	12		230
Collectively evaluated for impairment	1,238		1,017
Total allowance for loan and lease losses	1,250	1,250	1,247	1,235	1,230	1,225
Consumer [Member]
Loans and Leases Receivable Disclosure [Line Items]
Collectively evaluated for impairment	39,886		44,839
Total loans	39,886		44,839
Collectively evaluated for impairment	563		478
Total allowance for loan and lease losses	$ 563	$ 462	$ 478	$ 474	$ 463	$ 439