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Employee Benefits - Deferral Percentages (Details) | 12 Months Ended
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Dec. 31, 2020 plan
Employee Benefits |
Number of employee retirement plans | 2
401K Plan |
Employee Benefits |
Company contribution percentage of amounts deferred by employee's up to 3% of compensation | 100.00%
Company contribution percentage of amounts deferred by employee's between 3%-6% of compensation | 50.00%
401K Plan | Minimum |
Employee Benefits |
Percentage of eligible compensation | 3.00%
401K Plan | Maximum |
Employee Benefits |
Percentage of eligible compensation | 6.00%

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- Definition Percentage employer matches of the employee's percentage first three percent of eligible compensation. + References No definition available. + Details
Name: | alrs_DefinedContributionPlanEmployerMatchingContributionPercentOfMatchThresholdThreePercent
Namespace Prefix: | alrs_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage employer matches of the employee's percentage three to six percent of eligible compensation. + References No definition available. + Details
Name: | alrs_DefinedContributionPlanEmployerMatchingContributionPercentOfMatchThresholdThreeToSixPercent
Namespace Prefix: | alrs_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition The number of benefit plans. + References No definition available. + Details
Name: | alrs_NumberOfPlans
Namespace Prefix: | alrs_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

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- 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_DefinedBenefitPlanDisclosureLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan. + References No definition available. + Details
Name: | us-gaap_DefinedContributionPlanEmployerMatchingContributionPercent
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | us-gaap_RetirementPlanNameAxis=alrs_DefinedContributionSalaryReductionPlanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | srt_RangeAxis=srt_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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