Intangible Assets, Goodwill and Other (Narrative) (Details) - USD ($)	9 Months Ended
	Sep. 30, 2023	Feb. 28, 2023	Dec. 31, 2022
Goodwill [Line Items]
Goodwill	$ 1,029,234,000		$ 0
Finite-Lived Intangible Asset, Useful Life	10 years
Goodwill and Intangible Asset Impairment	$ 0
Umpqua Bank and Columbia Banking System Merger
Goodwill [Line Items]
Goodwill		$ 1,029,234,000