Loans and Other Real Estate - Impaired Loans with and without Specific Allowances (Detail) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
Sep. 30, 2020	Dec. 31, 2019
Financing Receivable, Impaired [Line Items]
Recorded Investment in Impaired Loans	$ 32,449	$ 22,124
Contractual Unpaid Principal Balance	33,734	22,776
Specific Allowance	223	352
Average Investment in Impaired Loans	29,214	18,342
Interest Income Recognized	288	426
Commercial, secured by real estate
Financing Receivable, Impaired [Line Items]
Loans without related allowance, Recorded Investment in Impaired Loans	24,396	12,478
Loans with related allowance, Recorded Investment in Impaired Loans	3,183	3,470
Recorded Investment in Impaired Loans	27,579	15,948
Loans without related allowance, Contractual Unpaid Principal Balance	25,015	12,630
Loans with related allowance, Contractual Unpaid Principal Balance	3,434	3,706
Contractual Unpaid Principal Balance	28,449	16,336
Specific Allowance	207	228
Loans without related allowance, Average Investment in Impaired Loans	20,863	10,386
Loans with related allowance, Average Investment in Impaired Loans	3,248	4,554
Average Investment in Impaired Loans	24,111	14,940
Loans without related allowance, Interest Income Recognized	119	164
Loans with related allowance, Interest Income Recognized	110	190
Interest Income Recognized	229	354
Commercial, industrial and other
Financing Receivable, Impaired [Line Items]
Loans without related allowance, Recorded Investment in Impaired Loans	1,632	1,391
Loans with related allowance, Recorded Investment in Impaired Loans	94	113
Recorded Investment in Impaired Loans	1,726	1,504
Loans without related allowance, Contractual Unpaid Principal Balance	1,628	1,381
Loans with related allowance, Contractual Unpaid Principal Balance	94	113
Contractual Unpaid Principal Balance	1,722	1,494
Specific Allowance	4	5
Loans without related allowance, Average Investment in Impaired Loans	1,312	1,334
Loans with related allowance, Average Investment in Impaired Loans	94	113
Average Investment in Impaired Loans	1,406	1,447
Loans without related allowance, Interest Income Recognized	11	16
Loans with related allowance, Interest Income Recognized	4	6
Interest Income Recognized	15	22
Equipment finance
Financing Receivable, Impaired [Line Items]
Loans without related allowance, Recorded Investment in Impaired Loans	0	0
Loans with related allowance, Recorded Investment in Impaired Loans	15	23
Recorded Investment in Impaired Loans	15	23
Loans without related allowance, Contractual Unpaid Principal Balance	0	0
Loans with related allowance, Contractual Unpaid Principal Balance	15	23
Contractual Unpaid Principal Balance	15	23
Specific Allowance	6	10
Loans without related allowance, Average Investment in Impaired Loans	0	0
Loans with related allowance, Average Investment in Impaired Loans	16	21
Average Investment in Impaired Loans	16	21
Loans without related allowance, Interest Income Recognized	0	0
Loans with related allowance, Interest Income Recognized	0	0
Interest Income Recognized	0	0
Real estate - residential mortgage
Financing Receivable, Impaired [Line Items]
Loans without related allowance, Recorded Investment in Impaired Loans	1,503	803
Loans with related allowance, Recorded Investment in Impaired Loans	337	1,512
Recorded Investment in Impaired Loans	1,840	2,315
Loans without related allowance, Contractual Unpaid Principal Balance	1,640	815
Loans with related allowance, Contractual Unpaid Principal Balance	525	1,682
Contractual Unpaid Principal Balance	2,165	2,497
Specific Allowance	2	104
Loans without related allowance, Average Investment in Impaired Loans	1,570	233
Loans with related allowance, Average Investment in Impaired Loans	582	926
Average Investment in Impaired Loans	2,152	1,159
Loans without related allowance, Interest Income Recognized	0	0
Loans with related allowance, Interest Income Recognized	12	19
Interest Income Recognized	12	19
Real estate - construction
Financing Receivable, Impaired [Line Items]
Loans without related allowance, Recorded Investment in Impaired Loans	694	1,663
Loans with related allowance, Recorded Investment in Impaired Loans	0	0
Recorded Investment in Impaired Loans	694	1,663
Loans without related allowance, Contractual Unpaid Principal Balance	694	1,661
Loans with related allowance, Contractual Unpaid Principal Balance	0	0
Contractual Unpaid Principal Balance	694	1,661
Specific Allowance	0	0
Loans without related allowance, Average Investment in Impaired Loans	926	82
Loans with related allowance, Average Investment in Impaired Loans	0	0
Average Investment in Impaired Loans	926	82
Loans without related allowance, Interest Income Recognized	10	2
Loans with related allowance, Interest Income Recognized	0	0
Interest Income Recognized	10	2
Home equity and consumer
Financing Receivable, Impaired [Line Items]
Loans without related allowance, Recorded Investment in Impaired Loans	0	0
Loans with related allowance, Recorded Investment in Impaired Loans	595	671
Recorded Investment in Impaired Loans	595	671
Loans without related allowance, Contractual Unpaid Principal Balance	0	0
Loans with related allowance, Contractual Unpaid Principal Balance	689	765
Contractual Unpaid Principal Balance	689	765
Specific Allowance	4	5
Loans without related allowance, Average Investment in Impaired Loans	0	0
Loans with related allowance, Average Investment in Impaired Loans	603	693
Average Investment in Impaired Loans	603	693
Loans without related allowance, Interest Income Recognized	0	0
Loans with related allowance, Interest Income Recognized	22	29
Interest Income Recognized	$ 22	$ 29

Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
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