RECENT DEVELOPMENTS AND SIGNIFICANT EVENTS RECENT DEVELOPMENTS AND SIGNIFICANT EVENTS (Details) (USD $) Share data in Millions, unless otherwise specified	0 Months Ended
	Nov. 05, 2014	Mar. 06, 2015	May 06, 2015 bank_branch	Mar. 31, 2015 state bank_branch
Business Acquisition [Line Items]
Number of branch offices in which entity operates				190
Number of states in which entity operates				5
AmericanWest Bank [Member]
Business Acquisition [Line Items]
Total assets acquired				4,600,000,000
Loans receivable				3,000,000,000
Deposits				3,700,000,000
Equity of acquired entity				586,000,000
Equity interests issued and issuable	13.23
Cash paid	130,000,000
Acquiree equity interest in acquirer	38.80%
Siuslaw Financial Group, Inc [Member]
Business Acquisition [Line Items]
Total assets acquired		370,306,000
Loans receivable		247,098,000
Deposits		316,406,000
Cash paid		$ 5,806,000
Subsequent Event [Member] | Siuslaw Financial Group, Inc [Member]
Business Acquisition [Line Items]
Number of branches acquired			10