Shareholders' Equity (Details) - USD ($) $ / shares in Units, $ in Millions				1 Months Ended	3 Months Ended	6 Months Ended
	Nov. 11, 2020	May 19, 2020	Feb. 21, 2019	Mar. 31, 2019	Jun. 30, 2021	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Business Acquisition Equity Interests Issued Or Issuable [Line Items]
Number of shares authorized to be repurchased					12,600,000	12,600,000
Purchase of treasury stock					$ 29.0	$ 41.7	$ 56.5
Treasury stock acquired, Shares,					400,000	600,000	1,700,000
Treasury Stock Acquired, Average Cost Per Share					$ 65.85	$ 64.60	$ 33.08
Stock Dividend	50.00%
Preferred stock, par value					$ 1	$ 1	$ 1.00	$ 1
Non-Cumulative Perpetual Preferred Stock, Series C [Member]
Business Acquisition Equity Interests Issued Or Issuable [Line Items]
Issuance of preferred stock		$ 225.0
Stock Dividend		6.125%
Preferred stock, par value		$ 1.00
Preferred stock liquidation preference per depositary share		25
Preferred stock, liquidation preference per share		$ 25,000
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
Stock Dividend			6.25%
Preferred stock, par value			$ 1.00
Preferred stock liquidation preference per depositary share			25
Preferred stock, liquidation preference per share			$ 25,000
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						2,400,000