Business Combinations and Asset Acquisitions - Schedule of purchase price (Details) - Umpqua Bank and Columbia Banking System Merger $ / shares in Units, shares in Thousands, $ in Thousands	Feb. 28, 2023 USD ($) $ / shares shares
Asset Acquisition [Line Items]
Business Acquisition Hypothetical Equity Interests Issued or Issuable | shares	349,515
Business Combination, Consideration Transferred	$ 2,339,278
Columbia Banking System, Inc.
Asset Acquisition [Line Items]
Business Acquisition Hypothetical Equity Interests Issued or Issuable | shares	132,365
Business Acquisition, Equity Interest Issued, RSUs Converted to Common Stock	$ 1,646
UHC
Asset Acquisition [Line Items]
Business Acquisition Hypothetical Equity Interests Issued or Issuable | shares	217,150
Business Acquisition Purchase Price | $ / shares	$ 17.66
Business Combination, Consideration Transferred, Equity Interests Issued and Issuable	$ 2,337,567
Business Acquisition, Equity Interest Issued or Issuable, Value Assigned	65
Business Combination, Consideration Transferred	$ 2,339,278