BANNER CORPORATION (PARENT COMPANY ONLY) (Statements of Cash Flows) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
OPERATING ACTIVITIES:
Net income	$ 201,048	$ 115,928	$ 146,278
Adjustments to reconcile net income to net cash provided from operating activities:
Decrease in deferred taxes	16,357	(13,963)	7,290
Net change in valuation of financial instruments carried at fair value	(4,616)	656	208
Stock-based compensation		9,168	7,142
Loss on extinguishment of debt	2,284	0	735
Net change in other assets	2,200	(27,559)	(10,171)
Net change in other liabilities	(11,083)	4,385	5,588
Net cash provided from operating activities	301,578	125,386	149,609
INVESTING ACTIVITIES:
Net cash used by investing activities	(1,015,426)	(1,454,624)	(143,114)
FINANCING ACTIVITIES:
Net proceeds from issuance of subordinated notes	0	98,027	0
Repayment of junior subordinated debentures	(8,248)	0	0
Proceeds from redemption of trust securities related to junior subordinated debentures	248	0	0
Taxes paid related to net share settlement for equity awards	(3,228)	(1,453)	(1,915)
Cash paid for repurchase of common stock	(56,528)	(31,775)	(53,922)
Cash dividends paid	(57,621)	(94,078)	(56,074)
Net cash provided from financing activities	1,613,965	2,255,686	29,044
CASH AND DUE FROM BANKS, BEGINNING OF YEAR	311,899
CASH AND DUE FROM BANKS, END OF YEAR	358,461	311,899
Banner Corporation
OPERATING ACTIVITIES:
Net income	201,048	115,928	146,278
Adjustments to reconcile net income to net cash provided from operating activities:
Equity in undistributed income of subsidiaries	(112,814)	(36,401)	(35,134)
Decrease in deferred taxes	(571)	1,438	6,969
Net change in valuation of financial instruments carried at fair value	55	0	0
Stock-based compensation	9,258	9,168	7,142
Loss on extinguishment of debt	2,284	0	0
Net change in other assets	(2,970)	16,756	2,594
Net change in other liabilities	4,050	(235)	(120)
Net cash provided from operating activities	100,340	106,654	127,729
INVESTING ACTIVITIES:
Other investing activities	(228)	(38)	(32)
Acquisitions	0	0	(442)
Net cash used by investing activities	(228)	(38)	410
FINANCING ACTIVITIES:
Net proceeds from issuance of subordinated notes	0	98,027	0
Repayment of junior subordinated debentures	(8,248)	0	0
Proceeds from redemption of trust securities related to junior subordinated debentures	248	0	0
Taxes paid related to net share settlement for equity awards	(3,228)	(1,453)	(1,915)
Cash paid for repurchase of common stock	(56,528)	(31,775)	(53,922)
Cash dividends paid	(57,621)	(94,078)	(56,074)
Net cash provided from financing activities	(125,377)	(29,279)	(111,911)
NET CHANGE IN CASH AND CASH EQUIVALENTS	(25,265)	77,337	16,228
CASH AND DUE FROM BANKS, BEGINNING OF YEAR	131,594	54,257	38,029
CASH AND DUE FROM BANKS, END OF YEAR	$ 106,329	$ 131,594	$ 54,257