XML 87 R70.htm IDEA: XBRL DOCUMENT
v3.20.4

Restrictions on Cash and Due from Banks (Details) - USD ($) $ in Millions | Dec. 31, 2020 | Dec. 31, 2019
--- | --- | ---
Restrictions on Cash and Due from Banks |  |
Amount of minimum average reserve balances required to be maintained | $ 0.0 | $ 13.8
Balances at the Federal Reserve Bank and other financial institutions | $ 145.6 | $ 109.4

X
- Definition Represents the amount of minimum average reserve balances required to be maintained. + References No definition available. + Details
Name: | alrs_AmountOfMinimumAverageReserveBalancesRequiredToBeMaintained
Namespace Prefix: | alrs_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition N/A + References No definition available. + Details
Name: | alrs_RestrictionsOnCashAndDueFromBanksAbstract
Namespace Prefix: | alrs_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of cash subject to withdrawal restrictions, restricted deposits held as compensating balances, and cash and securities segregated in compliance with regulations (such as cash deposited in a special reserve account for the exclusive benefit of customers). + References No definition available. + Details
Name: | us-gaap_CashAndSecuritiesSegregatedUnderFederalAndOtherRegulations
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant