BANNER CORPORATION (PARENT COMPANY ONLY) (Statements of Cash Flows) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
OPERATING ACTIVITIES:
Net income	$ 183,624	$ 195,378	$ 201,048
Adjustments to reconcile net income to net cash provided from operating activities:
Decrease in deferred taxes	1,514	7,624	16,357
Net change in valuation of financial instruments carried at fair value	4,218	(807)	(4,616)
Stock-based compensation	9,169	8,870	9,258
Gain (Loss) on Extinguishment of Debt	0	765	2,284
Net change in other assets	(8,968)	(39,028)	2,200
Net change in other liabilities	13,065	34,244	(11,083)
Net cash provided from operating activities	257,199	238,051	301,578
INVESTING ACTIVITIES:
Net cash provided from (used by) investing activities	191,929	(1,444,557)	(1,015,426)
FINANCING ACTIVITIES:
Repayment of junior subordinated debentures	0	(50,518)	(8,248)
Proceeds from redemption of trust preferred securities related to junior subordinated debentures	0	1,518	248
Taxes paid related to net share settlement of equity awards	(3,476)	(3,332)	(3,228)
Cash paid for repurchase of common stock	0	(10,960)	(56,528)
Cash dividends paid	(66,765)	(61,078)	(57,621)
Net cash (used by) provided from financing activities	(437,726)	(684,732)	1,613,965
NET CHANGE IN CASH AND CASH EQUIVALENTS	11,402	(1,891,238)	900,117
CASH AND DUE FROM BANKS, BEGINNING OF YEAR	198,154
CASH AND DUE FROM BANKS, END OF YEAR	209,634	198,154
Banner Corporation
OPERATING ACTIVITIES:
Net income	183,624	195,378	201,048
Adjustments to reconcile net income to net cash provided from operating activities:
Equity in undistributed income of subsidiaries	(92,018)	(104,391)	(112,814)
Decrease in deferred taxes	(52)	(43)	(571)
Net change in valuation of financial instruments carried at fair value	253	(56)	55
Stock-based compensation	9,169	8,870	9,258
Gain (Loss) on Extinguishment of Debt	0	765	2,284
Net change in other assets	442	(4,169)	(2,970)
Net change in other liabilities	(609)	3,765	4,050
Net cash provided from operating activities	100,809	100,119	100,340
INVESTING ACTIVITIES:
Other investing activities	488	(1,549)	(228)
Reduction in investment in subsidiaries	0	(3,072)	0
Net cash provided from (used by) investing activities	488	(4,621)	(228)
FINANCING ACTIVITIES:
Repayment of junior subordinated debentures	0	(50,518)	(8,248)
Proceeds from redemption of trust preferred securities related to junior subordinated debentures	0	1,518	248
Taxes paid related to net share settlement of equity awards	(3,476)	(3,332)	(3,228)
Cash paid for repurchase of common stock	0	(10,960)	(56,528)
Cash dividends paid	(66,765)	(61,078)	(57,621)
Net cash (used by) provided from financing activities	(70,241)	(124,370)	(125,377)
NET CHANGE IN CASH AND CASH EQUIVALENTS	31,056	(28,872)	(25,265)
CASH AND DUE FROM BANKS, BEGINNING OF YEAR	77,457	106,329	131,594
CASH AND DUE FROM BANKS, END OF YEAR	$ 108,513	$ 77,457	$ 106,329