BANNER CORPORATION (PARENT COMPANY ONLY) (Statements of Financial Position) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Oct. 01, 2015	Dec. 31, 2014	Dec. 31, 2013
ASSETS
Other assets	$ 59,466	$ 57,840
Total assets	9,793,668	9,796,298	$ 9,900,000
LIABILITIES AND SHAREHOLDERS’ EQUITY
Junior subordinated debentures at fair value	95,200	92,480
Shareholders’ equity	1,305,710	1,300,059		$ 582,888	$ 538,331
Total liabilities and stockholders' equity	9,793,668	9,796,298
Banner Corporation
ASSETS
Cash	86,268	58,232
Investment in trust equities	4,212	4,212
Investment in subsidiaries	1,307,475	1,319,348
Other assets	13,784	21,134
Total assets	1,411,739	1,402,926
LIABILITIES AND SHAREHOLDERS’ EQUITY
Miscellaneous liabilities	8,990	7,846
Deferred tax liability	1,839	2,541
Junior subordinated debentures at fair value	95,200	92,480
Shareholders’ equity	1,305,710	1,300,059
Total liabilities and stockholders' equity	$ 1,411,739	$ 1,402,926