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v3.23.1

Investment Securities - Proceeds from the call of held-to-maturity investment securities (Details) - USD ($) $ in Thousands | 3 Months Ended
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Mar. 31, 2023 | Mar. 31, 2022
Investment Securities |  |
Proceeds | $ 126 | $ 515

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- Definition The cash inflow associated with the sale or calls of securities that had been designated as held-to-maturity. + References No definition available. + Details
Name: | alrs_ProceedsFromSaleOrCallsOfHeldToMaturitySecurities
Namespace Prefix: | alrs_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- References No definition available. + Details
Name: | us-gaap_InvestmentsDebtAndEquitySecuritiesAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration