Fair Value of Assets and Liabilities - Deposits held for sale (Details) $ in Thousands	Jan. 15, 2019 item	Dec. 31, 2018 USD ($)
Fair Value of Assets and Liabilities
Number of branches whose deposits are to be sold \| item	2
Deposits held for sale \| $		$ 24,197

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

No definition available.

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