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Acquisitions - Schedule of Unaudited Pro Forma Revenue and Income (Details) - USD ($) $ / shares in Units, $ in Millions |  | 12 Months Ended
--- | --- | ---
Feb. 01, 2022 | Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021
Business Acquisition [Line Items] |  |  |  |
Estimated useful lives of related deposits |  | 12 years |  |
Business Acquisition, Pro Forma Earnings Per Share, Basic |  |  | $ 3.28 | $ 2.24
Business Acquisition, Pro Forma Earnings Per Share, Diluted |  |  | $ 3.28 | $ 2.24
Great Western Bank |  |  |  |
Business Acquisition [Line Items] |  |  |  |
Business Acquisition, Pro Forma Revenue |  |  | $ 1,223.3 | $ 1,200.9
Business Acquisition, Pro Forma Net Income (Loss) |  |  | $ 351.6 | $ 243.3
Core Deposits Intangibles |  |  |  |
Business Acquisition [Line Items] |  |  |  |
Estimated useful lives of related deposits | 10 years | 10 years |  |

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- Definition Weighted average amortization period of finite-lived intangible assets acquired either individually or as part of a group of assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 350 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (a)(3) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482665/350-30-50-1 + Details
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 5 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479907/805-20-50-5 + Details
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- Definition The pro forma basic net income per share for a period as if the business combination or combinations had been completed at the beginning of a period. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (h)(2) -SubTopic 10 -Topic 805 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479328/805-10-50-2 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (h)(3) -SubTopic 10 -Topic 805 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479328/805-10-50-2 + Details
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