BUSINESS COMBINATIONS BUSINESS COMBINATIONS (Schedule of Components of Acquisition) (Details) - USD ($) $ in Thousands	Oct. 01, 2015	Mar. 06, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Jun. 20, 2014	Dec. 31, 2013
LIABILITIES
Goodwill			$ 244,583	$ 247,738	$ 0		$ 0
Starbuck Bancshares, Inc [Member]
Business Acquisition [Line Items]
Effective date of acquisition	Oct. 01, 2015
Cash paid	$ 130,000
Fair value of common shares issued	630,674
Total consideration	760,674
ASSETS
Cash and cash equivalents	95,821
Securities	1,037,238
Loans receivable	2,999,130
REO, held for sale	6,105
Property and equipment	66,728
CDI	33,500
Deferred tax asset	108,454
Other assets	113,009
Total assets acquired	4,459,985
LIABILITIES
Deposits	3,638,596
FHLB advances	221,442
Junior subordinated debentures	5,806
Other liabilities	56,359
Total liabilities assumed	3,922,203
Net assets acquired	537,782
Goodwill	222,892
Contractual amount of acquired loans	$ 3,040,000
Siuslaw Financial Group, Inc [Member]
Business Acquisition [Line Items]
Effective date of acquisition		Mar. 06, 2015
Cash paid		$ 5,806
Fair value of common shares issued		58,100
Total consideration		63,906
ASSETS
Cash and cash equivalents		84,405
Securities		12,865
Loans receivable		247,098
REO, held for sale		2,525
Property and equipment		8,127
CDI		3,895
Other assets		10,848
Total assets acquired		369,763
LIABILITIES
Deposits		316,406
Junior subordinated debentures		5,959
Other liabilities		5,183
Total liabilities assumed		327,548
Net assets acquired		42,215
Goodwill		21,691
Contractual amount of acquired loans		$ 252,200
Six Oregon Branches [Member]
LIABILITIES
Contractual amount of acquired loans						$ 88,300