BANNER CORPORATION (PARENT COMPANY ONLY) (Statements of Financial Position) (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
ASSETS
Other assets	$ 171,471	$ 144,823
Total assets	16,804,872	15,031,623
LIABILITIES AND SHAREHOLDERS’ EQUITY
Subordinated notes, net	98,564	98,201
Junior subordinated debentures at fair value	119,815	116,974
Shareholders’ equity	1,690,327	1,666,264	$ 1,594,034	$ 1,478,595
Total liabilities and stockholders' equity	16,804,872	15,031,623
Banner Corporation
ASSETS
Cash	106,329	131,594
Investment in trust equities	4,196	4,444
Investment in subsidiaries	1,801,764	1,751,141
Other assets	5,877	2,852
Total assets	1,918,166	1,890,031
LIABILITIES AND SHAREHOLDERS’ EQUITY
Miscellaneous liabilities	5,723	2,170
Deferred tax liability, net	3,737	6,422
Subordinated notes, net	98,564	98,201
Junior subordinated debentures at fair value	119,815	116,974
Shareholders’ equity	1,690,327	1,666,264
Total liabilities and stockholders' equity	$ 1,918,166	$ 1,890,031