Investment Securities - Proceeds from the call of held-to-maturity investment securities (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2023	Mar. 31, 2022
Investment Securities
Proceeds	$ 126	$ 515

The cash inflow associated with the sale or calls of securities that had been designated as held-to-maturity.

No definition available.

Name:	alrs_ProceedsFromSaleOrCallsOfHeldToMaturitySecurities
Namespace Prefix:	alrs_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration