Shareholders' Equity (Details) - USD ($) $ / shares in Units, $ in Millions				1 Months Ended	3 Months Ended
	Nov. 11, 2020	May 19, 2020	Feb. 21, 2019	Mar. 31, 2019	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Business Acquisition Equity Interests Issued Or Issuable [Line Items]
Number of shares authorized to be repurchased					13,000,000.0
Purchase of treasury stock					$ 12.7	$ 56.2
Treasury stock acquired, Shares,					200,000	1,700,000
Treasury Stock Acquired, Average Cost Per Share					$ 61.91	$ 33.16
Preferred stock, dividend rate percentage	50.00%
Preferred stock, par value					$ 1	$ 1.00	$ 1
Stock Dividend	50.00%
Non-Cumulative Perpetual Preferred Stock, Series C [Member]
Business Acquisition Equity Interests Issued Or Issuable [Line Items]
Issuance of preferred stock		$ 225.0
Preferred stock, dividend rate percentage		6.125%
Preferred stock, par value		$ 1.00
Preferred stock liquidation preference per depositary share		25
Preferred stock, liquidation preference per share		$ 25,000
Stock Dividend		6.125%
Series C Preferred Stock [Member] | Over-Allotment Option [Member]
Business Acquisition Equity Interests Issued Or Issuable [Line Items]
Issuance of preferred stock		$ 25.0
Non-Cumulative Perpetual Preferred Stock, Series B [Member]
Business Acquisition Equity Interests Issued Or Issuable [Line Items]
Issuance of preferred stock			$ 150.0
Preferred stock, dividend rate percentage			6.25%
Preferred stock, par value			$ 1.00
Preferred stock liquidation preference per depositary share			25
Preferred stock, liquidation preference per share			$ 25,000
Stock Dividend			6.25%
Preferred stock, redemption terms					The Company may redeem the Series B preferred stock at its option, subject to regulatory approval, on or after March 15, 2024
Series B Preferred Stock [Member] | Over-Allotment Option [Member]
Business Acquisition Equity Interests Issued Or Issuable [Line Items]
Issuance of preferred stock				$ 10.0
Business Bancshares, Inc. [Member]
Business Acquisition Equity Interests Issued Or Issuable [Line Items]
Issuance of common stock					2,300,000