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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