BANNER CORPORATION (PARENT COMPANY ONLY) (Statements of Financial Position) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
ASSETS
Other assets	$ 74,108	$ 53,177
Total assets	11,871,317	9,763,209
LIABILITIES AND SHAREHOLDERS’ EQUITY
Junior subordinated debentures at fair value	114,091	98,707
Shareholders’ equity	1,478,595	1,272,626	$ 1,305,710	$ 1,300,059
Total liabilities and stockholders' equity	11,871,317	9,763,209
Banner Corporation
ASSETS
Cash	38,029	44,887
Investment in trust equities	4,212	4,212
Investment in subsidiaries	1,540,251	1,329,165
Other assets	25,267	3,072
Total assets	1,607,759	1,381,336
LIABILITIES AND SHAREHOLDERS’ EQUITY
Miscellaneous liabilities	15,073	9,607
Deferred tax liability	0	396
Junior subordinated debentures at fair value	114,091	98,707
Shareholders’ equity	1,478,595	1,272,626
Total liabilities and stockholders' equity	$ 1,607,759	$ 1,381,336