Note 6 - Debt Securities - Proceeds, Gains and Losses From Securities Available-for-sale (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Proceeds from sales of securities available-for-sale	$ 0	$ 3,385
Gross realized gains on securities available-for-sale	0	386
Gross realized losses on securities available-for-sale	$ 0	$ 0

The cash inflow associated with the sale of debt and equity securities classified as available-for-sale securities, including recorded in other assets pending settlement.

No definition available.

+ Details

Name:	atlo_ProceedsFromSaleOfAvailableForSaleSecuritiesIncludingRecordedInOtherAssetsPendingSettlement
Namespace Prefix:	atlo_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of realized gain on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 9
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27357-111563

+ Details

Name:	us-gaap_DebtSecuritiesAvailableForSaleRealizedGain
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of realized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

+ Details

Name:	us-gaap_DebtSecuritiesAvailableForSaleRealizedLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration