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