Capital Stock (Details) - USD ($) $ in Millions		3 Months Ended
	Feb. 01, 2022	Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022
Class of Stock [Line Items]
Shares outstanding (in shares)		104,382,018		104,442,023
Common shares issued (in shares)			46,887,104
Stock repurchased and retired (in shares)		55,080	37,698
Stock Repurchased and Retired During Period, Value		$ 1.8	$ 1.4
Common Stock, Shares, Issued		104,382,018		104,442,023
Great Western Bank
Class of Stock [Line Items]
Total consideration exchanged	$ 1,723.3
Class A Common Stock
Class of Stock [Line Items]
Shares outstanding (in shares)				104,442,023
Common Stock, Shares, Issued				104,442,023
Class A Common Stock | Great Western Bank
Class of Stock [Line Items]
Number of shares issued as consideration (in shares)	46,900,000