BANNER CORPORATION (PARENT COMPANY ONLY) (Statements of Operations) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
INTEREST INCOME:
Interest-bearing deposits	$ 576,005	$ 553,179	$ 496,891
OTHER INCOME (EXPENSE):
Other income	5,169	6,805	12,875
Interest on other borrowings	(3,376)	(377)	(467)
Other expenses	(23,723)	(24,869)	(24,236)
Income before provision for income taxes	227,087	240,775	246,594
PROVISION FOR INCOME TAXES	43,463	45,397	45,546
Net Income (Loss) Attributable to Parent	183,624	195,378	201,048
Banner Corporation
INTEREST INCOME:
Interest-bearing deposits	844	80	97
OTHER INCOME (EXPENSE):
Dividend income from subsidiaries	104,004	101,931	99,788
Equity in undistributed income of subsidiaries	92,018	104,391	112,814
Other income	1	96	146
Interest on other borrowings	(11,568)	(8,400)	(8,780)
Other expenses	(5,491)	(6,092)	(7,391)
Income before provision for income taxes	179,808	192,006	196,674
PROVISION FOR INCOME TAXES	(3,816)	(3,372)	(4,374)
Net Income (Loss) Attributable to Parent	$ 183,624	$ 195,378	$ 201,048