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Note 17 - Fair Value Measurements - Fair Value Quantitative Information (Details) - Fair Value, Nonrecurring [Member] - Fair Value, Inputs, Level 3 [Member] - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019
Evaluation of Collateral [Member] | Impaired Loan [Member] |  |
Estimated Fair Value | $ 10,306 | $ 535
Appraisal Valuation [Member] | Other Real Estate Owned [Member] |  |
Estimated Fair Value | $ 218 | $ 4,004
Appraisal Valuation [Member] | Other Real Estate Owned [Member] | Minimum [Member] |  |
Unobservable Inputs, Rate | 6.00% | 6.00%
Appraisal Valuation [Member] | Other Real Estate Owned [Member] | Maximum [Member] |  |
Unobservable Inputs, Rate | 8.00% | 8.00%
Appraisal Valuation [Member] | Other Real Estate Owned [Member] | Weighted Average [Member] |  |
Unobservable Inputs, Rate | (7.00%) | (7.00%)

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- Definition Percentage of estimation of value used as an input to measure fair value. + References No definition available. + Details
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Namespace Prefix: | atlo_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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- Definition Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258 + Details
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- Details
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- Details
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- Details
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- Details
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- Details
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- Details
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- Details
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- Details
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- Details
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