The Business of Sierra Bancorp - Additional Information (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019	Jan. 31, 1978
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Capital			$ 1,500
Assets	$ 3,110,044	$ 2,593,819
Cash, FDIC Insured Amount	$ 2,500,000