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Investment Securities - Proceeds from the call of held-to-maturity investment securities (Details) | 12 Months Ended
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Dec. 31, 2022 USD ($) security | Dec. 31, 2021 USD ($) security | Dec. 31, 2020 USD ($)
Investment Securities |  |  |
Proceeds | $ 963,000 | $ 1,772,000 |
Realized gains |  | $ 11,000 |
Number of held to maturity securities sold | 0 | 1 | 0
Amortized Cost |  | $ 330,000 |
Proceeds from sales of investment securities held-to-maturity |  | $ 348,000 |

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- Definition Amortized cost of investment securities held to maturity. + References No definition available. + Details
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Namespace Prefix: | alrs_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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- Definition Amount of gain on sale of investment in debt security measured at amortized cost (held-to-maturity), including other-than-temporary impairment (OTTI). + References No definition available. + Details
Name: | alrs_DebtSecuritiesHeldToMaturitySoldRealizedGain
Namespace Prefix: | alrs_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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- Definition Number of held to maturity securities sold during the period. + References No definition available. + Details
Name: | alrs_NumberOfHeldToMaturitySecuritiesSold
Namespace Prefix: | alrs_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

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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
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
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- Definition The cash inflow associated with the sale of securities that had been designated as held-to-maturity. Excludes proceeds from maturities, prepayments and calls by the issuer. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 11 -URI https://asc.fasb.org/extlink&oid=124260329&loc=d3e26853-111562 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 12 -Subparagraph (a) -URI https://asc.fasb.org/extlink&oid=126954810&loc=d3e3179-108585 + Details
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Period Type: | duration