Value of principal and interest deferrals in connection with the CARES Act.

No definition available.

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

- Definition

Number of principal and interest deferrals in connection with the CARES Act.

+ References

No definition available.

+ Details

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Namespace Prefix:	alrs_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Typical loan deferral period under the CARES Act.

+ References

No definition available.

+ Details

Name:	alrs_PeriodOfLoanPrincipalAndInterestDeferrals
Namespace Prefix:	alrs_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of specific reserve for loans and losses allocated.

+ References

No definition available.

+ Details

Name:	alrs_SpecificReserveForLoansAndLeasesAllocated
Namespace Prefix:	alrs_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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

- Definition

Number of financing receivables that have been modified by troubled debt restructurings.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=118936363&loc=SL6953676-111524

+ Details

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Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount, after troubled debt restructuring, of modified financing receivable.

+ References

+ Details

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

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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Period Type:

Loans and Allowance for Loan Losses - Troubled Debt Restructurings (Details) $ in Millions	1 Months Ended	3 Months Ended		12 Months Ended
	Apr. 21, 2020 USD ($) loan	Mar. 31, 2020 loan	Mar. 31, 2019 loan	Dec. 31, 2019 USD ($)
Troubled debt restructuring
Number of loans modified as modified as a troubled debt restructuring \| loan		0
Number of principal and interest deferrals in connection with the CARES Act \| loan	325
Loan principal and interest deferrals in connection with the CARES Act \| $	$ 97.4
Maximum
Troubled debt restructuring
Typical loan deferral period under the CARES Act	90 days
Interest Rate Below Market Reduction
Troubled debt restructuring
Number of loans modified as modified as a troubled debt restructuring \| loan			1
Carrying value of restructured loan \| $				$ 0.2
Specific reserve for loan losses allocated \| $				$ 0.0