BANNER CORPORATION (PARENT COMPANY ONLY) (Statements of Operations) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended												12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
INTEREST INCOME:
Interest-bearing deposits	$ 41,607	$ 41,893	$ 42,248	$ 40,968	$ 41,534	$ 42,698	$ 42,290	$ 41,126	$ 41,586	$ 41,728	$ 41,201	$ 40,056	$ 166,716	$ 167,648	$ 164,571
OTHER INCOME (EXPENSE):
Dividend income from subsidiaries													18	0	0
Other income													3,484	4,697	2,511
Other expenses													(12,474)	(12,795)	(12,135)
Income before provision for (benefit from) income taxes	17,258	17,545	17,414	16,866	19,326	18,027	(6,440)	9,184	5,070	6,030	2,199	(7,842)	69,083	40,097	5,457
PROVISION FOR (BENEFIT FROM) INCOME TAXES	5,704	5,880	5,661	5,284	4,638	2,407	(31,830)	0	0	0	0	0	22,528	(24,785)	0
NET INCOME	11,554	11,665	11,753	11,582	14,688	15,620	25,390	9,184	5,070	6,030	2,199	(7,842)	46,555	64,882	5,457
PREFERRED STOCK DIVIDEND AND DISCOUNT ACCRETION
Preferred stock dividend	0	0	0	0	611	1,227	1,550	1,550	1,550	1,550	1,550	1,550	0	4,938	6,200
Preferred stock discount accretion	0	0	0	0	1,174	1,216	454	454	425	425	425	426	0	3,298	1,701
Gain on repurchase of preferred stock	0	0	0	0	(401)	(2,070)	0	0	0	0	0	0	0	(2,471)	0
NET INCOME (LOSS) AVAILABLE TO COMMON SHAREHOLDERS	11,554	11,665	11,753	11,582	13,304	15,247	23,386	7,180	3,095	4,055	224	(9,818)	46,555	59,117	(2,444)
Banner Corporation
INTEREST INCOME:
Interest-bearing deposits													82	218	277
OTHER INCOME (EXPENSE):
Dividend income from subsidiaries													24,725	61,329	990
Equity in undistributed income of subsidiaries													23,994	23,507	9,478
Other income													3,016	55	46
Net change in valuation of financial instruments carried at fair value													(865)	(23,075)	(1,563)
Interest on other borrowings													(2,968)	(3,395)	(4,193)
Other expenses													(2,794)	(2,375)	(2,313)
Income before provision for (benefit from) income taxes													45,190	56,264	2,722
PROVISION FOR (BENEFIT FROM) INCOME TAXES													(1,365)	(8,618)	(2,735)
NET INCOME													46,555	64,882	5,457
PREFERRED STOCK DIVIDEND AND DISCOUNT ACCRETION
Preferred stock dividend													0	4,938	6,200
Preferred stock discount accretion													0	3,298	1,701
Gain on repurchase of preferred stock													0	(2,471)	0
NET INCOME (LOSS) AVAILABLE TO COMMON SHAREHOLDERS													$ 46,555	$ 59,117	$ (2,444)