Stock-Based Compensation Plans (Information Regarding Restricted Shares) (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
General vesting period (years)	3 years
Unearned compensation costs	$ 19.2	$ 18.5
Recognition of unearned compensation, (years)	1 year
Fair value of Restricted Shares vested	$ 28.7	24.2	$ 23.5
Stock-based compensation expense	30.5	27.8	25.5
Related income tax benefit	(6.9)	(6.3)	(5.8)
Net stock-based compensation expense	$ 23.6	$ 21.5	$ 19.7
Shares
Outstanding — beginning of year (in shares)	1,741,486
Granted (in shares)	823,703
Vested (in shares)	(787,870)
Canceled (in shares)	(110,636)
Outstanding — ending of year (in shares)	1,666,683	1,741,486
Weighted Average Grant-Date Fair Value
Outstanding — beginning of year (in dollars per share)	$ 36.06
Granted (in dollars per share)	42.73
Vested (in dollars per share)	36.40
Canceled (in dollars per share)	36.30
Outstanding — ending of year (in dollars per share)	$ 39.18	$ 36.06
Restricted Stock | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
General expiration period, from date of grant or time of termination (years)	1 year
General vesting period (years)	1 year
Restricted Stock | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
General expiration period, from date of grant or time of termination (years)	3 years
General vesting period (years)	3 years
Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
General vesting period (years)	36 months
Shares
Outstanding — ending of year (in shares)	520,000
Weighted Average Grant-Date Fair Value
Estimated vesting of shares based on performance shares	520,000
Performance Shares | Minimum
Weighted Average Grant-Date Fair Value
Estimated vesting of shares based on performance shares	0
Performance Shares | Maximum
Weighted Average Grant-Date Fair Value
Estimated vesting of shares based on performance shares	1,196,000