BUSINESS COMBINATIONS BUSINESS COMBINATIONS (Textual) (Details) $ / shares in Units, $ in Thousands				3 Months Ended		9 Months Ended
	Oct. 01, 2015 USD ($)	Mar. 06, 2015 USD ($) bank_branch $ / shares	Jun. 20, 2014 USD ($) location	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Business Acquisition [Line Items]
Goodwill				$ 21,148		$ 21,148		$ 0	$ 0
Bargain purchase gain on acquisition				$ 0	$ 0	$ 0	$ (9,079)
Siuslaw Financial Group, Inc [Member]
Business Acquisition [Line Items]
Acquisition Date		Mar. 06, 2015
Number of branches acquired | bank_branch		10
Cash paid in acquisition		$ 5,806
Fair value of common shares issued		$ 58,100
Equity interest issued to Siuslaw's shareholders per share | $ / shares		$ 0.32231
Cash payment issued to Siuslaw's shareholders (usd per share) | $ / shares		$ 1.41622
Business Combination, Consideration Transferred		$ 63,906
Total assets acquired		370,306
Loans receivable acquired		247,098
Goodwill		21,148
Core deposit intangible		3,895
Deposits acquired		316,406
Acquired finite-lived intangible assets, weighted average useful life						8 years
Acquired receivables, non-credit-impaired		244,200
Acquired receivables, non-credit-impaired, fair value		241,400
Acquired receivables, discount		$ (2,800)
Six Oregon Branches [Member]
Business Acquisition [Line Items]
Acquisition Date			Jun. 20, 2014
Number of branches acquired | location			6
Business Combination, Consideration Transferred			$ 0
Total assets acquired			221,206
Loans receivable acquired			87,923
Core deposit intangible			2,372
Deposits acquired			212,085
Acquired finite-lived intangible assets, weighted average useful life						8 years
Bargain purchase gain on acquisition			(9,079)
Bargain purchase discount			7,000
Net fair value adjustments on acquired assets and liabilities			$ (300)
Business Acquisition [Member] | Starbuck Bancshares, Inc [Member]
Business Acquisition [Line Items]
Acquisition Date	Oct. 01, 2015
Fair value of common shares issued	$ 630,700
Business Combination, Consideration Transferred	760,700
Total assets acquired	4,500,000
Loans receivable acquired	3,000,000
Deposits acquired	$ 3,600,000