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Business Combinations and Asset Acquisitions - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023	Feb. 28, 2023
Asset Acquisition [Line Items]
Goodwill	$ 1,029,234		$ 1,029,234		$ 1,029,234
Business Combination, Acquisition Related Costs	2,364	$ 18,938	21,483	$ 164,485
Umpqua Bank and Columbia Banking System Merger
Asset Acquisition [Line Items]
Goodwill						$ 1,000,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill						$ 710,200
Business Combination, Acquisition Related Costs	$ 1,600	$ 18,900	$ 8,800	$ 164,500

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This element represents acquisition-related costs incurred to effect a business combination which costs have been expensed during the period. Such costs include finder's fees; advisory, legal, accounting, valuation, and other professional or consulting fees; general administrative costs, including the costs of maintaining an internal acquisitions department; and may include costs of registering and issuing debt and equity securities.

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Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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