Business Combinations and Asset Acquisitions - Schedule of hypothetical number of shares (Details) - Umpqua Bank and Columbia Banking System Merger shares in Thousands	Feb. 28, 2023 shares
Asset Acquisition [Line Items]
Business Acquisition Hypothetical Equity Interests Issued or Issuable	349,515
Business Acquisition Hypothetical Percentage of Voting Interests Acquired	1.000
Columbia Banking System, Inc.
Asset Acquisition [Line Items]
Business Acquisition Hypothetical Equity Interests Issued or Issuable	132,365
Business Acquisition Hypothetical Percentage of Voting Interests Acquired	0.379
UHC
Asset Acquisition [Line Items]
Business Acquisition Hypothetical Equity Interests Issued or Issuable	217,150
Business Acquisition Hypothetical Percentage of Voting Interests Acquired	0.621