BANNER CORPORATION (PARENT COMPANY ONLY) (Statements of Financial Position) (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
ASSETS
Other assets	$ 211,481	$ 177,362
Total assets	15,670,391	15,833,431
LIABILITIES AND SHAREHOLDERS’ EQUITY
Subordinated notes, net	92,851
Junior subordinated debentures at fair value	66,413	74,857
Shareholders’ equity	1,652,691	1,456,432	$ 1,690,327	$ 1,666,264
Total liabilities and stockholders' equity	15,670,391	15,833,431
Banner Corporation
ASSETS
Cash	108,513	77,457
Investment in trust equities	2,678	2,678
Investment in subsidiaries	1,709,153	1,549,918
Other assets	10,467	11,651
Total assets	1,830,811	1,641,704
LIABILITIES AND SHAREHOLDERS’ EQUITY
Miscellaneous liabilities	7,838	8,925
Deferred tax liability, net	4,518	2,543
Subordinated notes, net	99,351	98,947
Junior subordinated debentures at fair value	66,413	74,857
Shareholders’ equity	1,652,691	1,456,432
Total liabilities and stockholders' equity	$ 1,830,811	$ 1,641,704