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Allowance for Loan Losses - Additional Information (Details) - USD ($) | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2018 | Jun. 30, 2017 | Jun. 30, 2018 | Jun. 30, 2017
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |
Loans considered nonperforming (in days) |  |  | 90 days |
Threshold for evaluation for impairment of substandard and nonaccrual commercial loans | $ 500,000.0 |  | $ 500,000.0 |
Change-off arising from participation loan agreement | 8,632,000 | $ 5,822,000 | 10,076,000 | $ 8,763,000
Other consumer |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |
Change-off arising from participation loan agreement | 414,000 | $ 370,000 | 872,000 | $ 804,000
Other consumer | Vehicles and Equipment Liens |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |
Change-off arising from participation loan agreement | 5,200,000 |  | 5,200,000 |
Participating loans, total exposure | 4,900,000 |  | 4,900,000 |
Participating loans, direct exposure | $ 950,000 |  | $ 950,000 |

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- Definition Minimum amount over which evaluation for impairment of substandard and nonaccrual commercial loans are made. + References No definition available. + Details
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- Definition Participating Loans, Direct Exposure + References No definition available. + Details
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- Definition Participating Loans, Total Exposure + References No definition available. + Details
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- Definition Amount of loans and leases that have been written off from both loan receivables and allowance reserve for credit loss. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (c)(3) -URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953423-111524 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.7(d)) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 + Details
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- Definition 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. + References No definition available. + Details
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