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Cash and Cash Equivalents	12 Months Ended
Cash and Cash Equivalents	Dec. 31, 2017
Banking and Thrift [Abstract]
Cash and Cash Equivalents	Cash and Cash Equivalents The Bank is required to maintain an average reserve balance with the Federal Reserve Bank or maintain such reserve balance in the form of cash. The amount of required reserve balance at December 31, 2017 and 2016 was approximately $163.4 million and $138.4 million, respectively, and was met by holding cash and maintaining an average balance with the Federal Reserve Bank. Umpqua had restricted cash included in cash and due from banks on the balance sheet of $27.9 million as of December 31, 2017, and $51.0 million as of December 31, 2016, relating mostly to collateral required on interest rate swaps as discussed in Note 19.