Note 12 - Earnings Per Share (Details Textual)	12 Months Ended
Dec. 31, 2019
Number Of Forms Of Outstanding Common Stock	2

Represents the number of forms of outstanding stock awards available with the entity.

No definition available.

Name:	ovly_NumberOfFormsOfOutstandingCommonStock
Namespace Prefix:	ovly_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration