Number of loans charged-off.

No definition available.

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

- Definition

The percentage of increase in amount excluding accrued interest, of allowance for credit loss on financing receivable.

+ References

No definition available.

+ Details

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Namespace Prefix:	alrs_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of increase in allowance for credit loss on accounts receivable, from recovery.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479319/326-20-50-13

+ Details

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

- Definition

Amount of expense (reversal of expense) for expected credit loss on investment in debt security measured at amortized cost (held-to-maturity).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479319/326-20-50-13

+ Details

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

- Definition

Amount excluding accrued interest, of allowance for credit loss on financing receivable. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479344/326-20-45-1

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

+ Details

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

- Definition

Amount, excluding accrued interest, of increase (decrease) in allowance for credit loss on financing receivable. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479319/326-20-50-13

+ Details

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

- Definition

Amount, excluding accrued interest, of decrease in allowance for credit loss on financing receivable from writeoff. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479319/326-20-50-6

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479319/326-20-50-13

+ Details

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

- Definition

Amount, excluding accrued interest, of credit loss expense (reversal of expense) on financing receivable. Excludes net investment in lease.

+ References

+ Details

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

- Definition

Amount of expense (reversal of expense) for expected credit loss for off-balance sheet credit exposure. Excludes off-balance sheet credit exposure accounted for as insurance and instrument accounted for under derivatives and hedging.

+ References

+ Details

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

Loans and Allowance for Credit Losses - Changes in allowance (Details) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2024 USD ($)	Jun. 30, 2023 USD ($)	Jun. 30, 2024 USD ($) loan	Jun. 30, 2023 USD ($)	Dec. 31, 2023 USD ($)
Changes in the allowance
Beginning balance	$ 36,584	$ 35,102	$ 35,843	$ 31,146	$ 31,146
Provision for credit losses	4,270		5,069	460
Loan charge-offs	(2,734)	(108)	(2,939)	(365)	(613)
Loan recoveries	212	511	359	598
Ending balance	38,332	35,696	38,332	35,696	35,843
Provision (recovery) for off-balance sheet credit loss	275	186	(518)	44
Debt securities held-to-maturity credit loss (reversal)	(56)	5	(62)	46
Increase (decrease) in allowance for credit loss			$ 2,500
Percentage of increase in ACL compared to previous year			6.90%
Adoption of CECL \| Cumulative Effect, Period of Adoption, Adjustment
Changes in the allowance
Beginning balance			$ 3,857
Provision for credit losses		191
Ending balance					3,857
Commercial
Changes in the allowance
Beginning balance	28,610	25,154	27,971	23,472	23,472
Provision for credit losses	4,972		5,670	140
Loan charge-offs	(2,730)	(85)	(2,923)	(260)
Loan recoveries	128	450	262	517
Ending balance	30,980	25,581	30,980	25,581	27,971
Commercial \| Adoption of CECL \| Cumulative Effect, Period of Adoption, Adjustment
Changes in the allowance
Beginning balance			1,712
Provision for credit losses		62
Ending balance					1,712
Commercial \| Construction, land and development and non-owner occupied
Changes in the allowance
Increase (decrease) in allowance for credit loss			5,700
Commercial \| Commercial and industrial
Changes in the allowance
Beginning balance	9,508	7,954	9,705	8,690	8,690
Provision for credit losses	(663)		(819)	(219)
Loan charge-offs	(2,730)	(85)	(2,894)	(260)	(436)
Loan recoveries	119	438	242	494
Ending balance	6,234	8,170	6,234	8,170	9,705
Increase (decrease) in allowance for credit loss			$ (2,600)
Number of loans charged-off \| loan			1
Commercial \| Commercial and industrial \| Adoption of CECL \| Cumulative Effect, Period of Adoption, Adjustment
Changes in the allowance
Beginning balance			$ (535)
Provision for credit losses		(137)
Ending balance					(535)
Commercial \| Commercial real estate
Changes in the allowance
Beginning balance	18,635	16,856	18,086	14,251	14,251
Provision for credit losses	5,658		6,225	489
Loan charge-offs			(29)
Loan recoveries	9	11	20	22
Ending balance	24,302	17,171	24,302	17,171	18,086
Commercial \| Commercial real estate \| Adoption of CECL \| Cumulative Effect, Period of Adoption, Adjustment
Changes in the allowance
Beginning balance			2,409
Provision for credit losses		304
Ending balance					2,409
Commercial \| Commercial real estate \| Construction, land and development
Changes in the allowance
Beginning balance	5,922	4,349	6,135	1,458	1,458
Provision for credit losses	4,898		4,685	(278)
Ending balance	10,820	3,731	10,820	3,731	6,135
Commercial \| Commercial real estate \| Construction, land and development \| Adoption of CECL \| Cumulative Effect, Period of Adoption, Adjustment
Changes in the allowance
Beginning balance			2,551
Provision for credit losses		(618)
Ending balance					2,551
Commercial \| Commercial real estate \| Multifamily
Changes in the allowance
Beginning balance	2,148	1,562	1,776	1,062	1,062
Provision for credit losses	282		654	1,091
Ending balance	2,430	1,991	2,430	1,991	1,776
Commercial \| Commercial real estate \| Multifamily \| Adoption of CECL \| Cumulative Effect, Period of Adoption, Adjustment
Changes in the allowance
Beginning balance			(162)
Provision for credit losses		429
Ending balance					(162)
Commercial \| Commercial real estate \| Non-owner occupied
Changes in the allowance
Beginning balance	8,104	8,045	7,726	7,543	7,543
Provision for credit losses	668		1,046	(332)
Ending balance	8,772	8,555	8,772	8,555	7,726
Commercial \| Commercial real estate \| Non-owner occupied \| Adoption of CECL \| Cumulative Effect, Period of Adoption, Adjustment
Changes in the allowance
Beginning balance			1,344
Provision for credit losses		510
Ending balance					1,344
Commercial \| Commercial real estate \| Owner occupied
Changes in the allowance
Beginning balance	2,461	2,900	2,449	4,188	4,188
Provision for credit losses	(190)		(160)	8
Loan charge-offs			(29)
Loan recoveries	9	11	20	22
Ending balance	2,280	2,894	2,280	2,894	2,449
Commercial \| Commercial real estate \| Owner occupied \| Adoption of CECL \| Cumulative Effect, Period of Adoption, Adjustment
Changes in the allowance
Beginning balance			(1,324)
Provision for credit losses		(17)
Ending balance					(1,324)
Agricultural \| Commercial real estate
Changes in the allowance
Beginning balance	467	344	180	531	531
Provision for credit losses	(23)		264	(130)
Loan recoveries		1		1
Ending balance	444	240	444	240	180
Agricultural \| Commercial real estate \| Adoption of CECL \| Cumulative Effect, Period of Adoption, Adjustment
Changes in the allowance
Beginning balance			(162)
Provision for credit losses		(105)
Ending balance					(162)
Agricultural \| Commercial real estate \| Land
Changes in the allowance
Beginning balance	248	192	96	281	281
Provision for credit losses	11		163	(59)
Loan recoveries		1		1
Ending balance	259	137	259	137	96
Agricultural \| Commercial real estate \| Land \| Adoption of CECL \| Cumulative Effect, Period of Adoption, Adjustment
Changes in the allowance
Beginning balance			(86)
Provision for credit losses		(56)
Ending balance					(86)
Agricultural \| Commercial real estate \| Production
Changes in the allowance
Beginning balance	219	152	84	250	250
Provision for credit losses	(34)		101	(71)
Ending balance	185	103	185	103	84
Agricultural \| Commercial real estate \| Production \| Adoption of CECL \| Cumulative Effect, Period of Adoption, Adjustment
Changes in the allowance
Beginning balance			(76)
Provision for credit losses		(49)
Ending balance					(76)
Consumer
Changes in the allowance
Beginning balance	7,974		7,872	7,674	7,674
Provision for credit losses	(702)		(601)	320
Loan charge-offs	(4)		(16)	(105)
Loan recoveries	84		97	81
Ending balance	7,352	10,115	7,352	10,115	7,872
Consumer \| Adoption of CECL \| Cumulative Effect, Period of Adoption, Adjustment
Changes in the allowance
Beginning balance			2,145
Ending balance					2,145
Consumer \| Commercial real estate \| Junior lien
Changes in the allowance
Loan charge-offs					(77)
Consumer \| Residential
Changes in the allowance
Beginning balance	7,789	9,625	7,671	7,143	7,143
Provision for credit losses	(836)		(718)	442
Loan charge-offs	(3)		(3)	(77)
Loan recoveries	74	46	74	54
Ending balance	7,024	9,804	7,024	9,804	7,671
Consumer \| Residential \| Adoption of CECL \| Cumulative Effect, Period of Adoption, Adjustment
Changes in the allowance
Beginning balance			2,242
Provision for credit losses		133
Ending balance					2,242
Consumer \| Residential \| First lien
Changes in the allowance
Beginning balance	6,152	7,389	6,087	5,495	5,495
Provision for credit losses	(786)		(721)	274
Loan charge-offs					(9)
Loan recoveries				2
Ending balance	5,366	7,571	5,366	7,571	6,087
Consumer \| Residential \| First lien \| Adoption of CECL \| Cumulative Effect, Period of Adoption, Adjustment
Changes in the allowance
Beginning balance			1,800
Provision for credit losses		182
Ending balance					1,800
Consumer \| Residential \| Construction
Changes in the allowance
Beginning balance	489	908	485	345	345
Provision for credit losses	(31)		(27)	(28)
Ending balance	458	785	458	785	485
Consumer \| Residential \| Construction \| Adoption of CECL \| Cumulative Effect, Period of Adoption, Adjustment
Changes in the allowance
Beginning balance			468
Provision for credit losses		(123)
Ending balance					468
Consumer \| Residential \| HELOC
Changes in the allowance
Beginning balance	864	1,038	835	951	951
Provision for credit losses	22		51	104
Loan charge-offs					(40)
Loan recoveries				3
Ending balance	886	1,117	886	1,117	835
Consumer \| Residential \| HELOC \| Adoption of CECL \| Cumulative Effect, Period of Adoption, Adjustment
Changes in the allowance
Beginning balance			59
Provision for credit losses		79
Ending balance					59
Consumer \| Residential \| Junior lien
Changes in the allowance
Beginning balance	284	290	264	352	352
Provision for credit losses	(41)		(21)	92
Loan charge-offs	(3)		(3)	(77)
Loan recoveries	74	46	74	49
Ending balance	314	331	314	331	264
Consumer \| Residential \| Junior lien \| Adoption of CECL \| Cumulative Effect, Period of Adoption, Adjustment
Changes in the allowance
Beginning balance			(85)
Provision for credit losses		(5)
Ending balance					(85)
Consumer \| Other consumer \| Other consumer
Changes in the allowance
Beginning balance	185	323	201	531	531
Provision for credit losses	134		117	(122)
Loan charge-offs	(1)	(23)	(13)	(28)	(51)
Loan recoveries	10	15	23	27
Ending balance	$ 328	311	328	311	201
Consumer \| Other consumer \| Other consumer \| Adoption of CECL \| Cumulative Effect, Period of Adoption, Adjustment
Changes in the allowance
Beginning balance			$ (97)
Provision for credit losses		(4)
Ending balance					$ (97)
Consumer \| Unallocated
Changes in the allowance
Beginning balance		9,948
Loan charge-offs		(23)
Loan recoveries		61
Ending balance		10,115		$ 10,115
Consumer \| Unallocated \| Adoption of CECL \| Cumulative Effect, Period of Adoption, Adjustment
Changes in the allowance
Provision for credit losses		$ 129