Fair Value of Assets and Liabilities - Loans Held for Sale (Details) $ in Thousands	Jan. 15, 2019 item	Dec. 31, 2018 USD ($)
Fair Value of Assets and Liabilities
Number of branches whose loans are to be sold \| item	2
Loans held for branch sale \| $		$ 32,031

Represents the number of branches whose loans are agreed to be sold during the period.

No definition available.

Name:	alrs_NumberOfBranchesWhoseLoansAreSold
Namespace Prefix:	alrs_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration