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Business Combinations and Asset Acquisitions - Pro Forma (Details) - Umpqua Bank and Columbia Banking System Merger $ in Thousands	9 Months Ended
	Sep. 30, 2023 USD ($)
Asset Acquisition [Line Items]
Business acquisition, pro forma net interest income	$ 1,494,339
Business Acquisition, Pro Forma Non-interest Income	172,231
Business Acquisition, Pro Forma Net Income (Loss)	530,049
Business Combination, Acquisition Related Costs - Combined for proforma	$ 192,500

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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 805
-SubTopic 50
-Name Accounting Standards Codification
-Section 15
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480123/805-50-15-3

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The pro forma net Income or Loss for the period as if the business combination or combinations had been completed at the beginning of a period.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 805
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (h)(2)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479328/805-10-50-2

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