Investment Securities - Proceeds from the call of held-to-maturity investment securities (Details)	12 Months Ended
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

Amortized cost of investment securities held to maturity.

No definition available.

Name:	alrs_DebtSecuritiesHeldToMaturityAmortizedCost
Namespace Prefix:	alrs_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- 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

- 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

- 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

- References

No definition available.

+ Details

Name:	us-gaap_InvestmentsDebtAndEquitySecuritiesAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- 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

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