BANNER CORPORATION (PARENT COMPANY ONLY) (Statements of Cash Flows) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
OPERATING ACTIVITIES:
Net income (loss)	$ 64,882	$ 5,457	$ (61,896)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Increase (decrease) in deferred taxes	(35,007)	0	14,988
Net change in valuation of financial instruments carried at fair value	16,515	624	(1,747)
Increase in other assets	(869)	17,965	15,622
Increase (decrease) in other liabilities	3,569	2,104	(2,020)
Net cash provided from operating activities	81,415	101,313	114,519
INVESTING ACTIVITIES:
Net cash provided from (used by) investing activities	52,479	(171,213)	176,054
FINANCING ACTIVITIES
Issuance of stock for stockholder reinvestment program	36,317	21,556	16,201
Redemption of preferred stock	(121,528)	0	0
Issuance of stock in secondary offering, net of costs	0	0	161,637
Cash dividends paid	(6,470)	(8,827)	(8,867)
Net cash used by financing activities	(85,032)	(159,316)	(251,926)
NET INCREASE (DECREASE) IN CASH AND DUE FROM BANKS	48,862	(229,216)	38,647
CASH AND DUE FROM BANKS, BEGINNING OF YEAR	132,436	361,652	323,005
CASH AND DUE FROM BANKS, END OF YEAR	181,298	132,436	361,652
Banner Corporation
OPERATING ACTIVITIES:
Net income (loss)	64,882	5,457	(61,896)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Equity in undistributed earnings of subsidiaries	(23,507)	(9,478)	58,766
Increase (decrease) in deferred taxes	(13,030)	(562)	703
Net change in valuation of financial instruments carried at fair value	23,075	1,563	730
Increase in other assets	(496)	1,933	(847)
Increase (decrease) in other liabilities	4,941	(957)	3
Net cash provided from operating activities	55,865	(2,044)	(2,541)
INVESTING ACTIVITIES:
Funds transferred to deferred compensation trust	(332)	(162)	(110)
Additional funds invested in subsidiaries	0	0	(110,000)
Net cash provided from (used by) investing activities	(332)	(162)	(110,110)
FINANCING ACTIVITIES
Issuance of stock for stockholder reinvestment program	36,316	21,556	16,201
Redemption of preferred stock	(121,528)	0	0
Issuance of stock in secondary offering, net of costs	0	0	161,637
Cash dividends paid	(6,470)	(8,827)	(8,867)
Net cash used by financing activities	(91,682)	12,729	168,971
NET INCREASE (DECREASE) IN CASH AND DUE FROM BANKS	(36,149)	10,523	56,320
CASH AND DUE FROM BANKS, BEGINNING OF YEAR	73,033	62,510	6,190
CASH AND DUE FROM BANKS, END OF YEAR	$ 36,884	$ 73,033	$ 62,510