Employee Stock and Incentive Plans - Share-Based Compensation Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share-Based Compensation Expense [Line Items]
Total Share-Based Compensation Expense	$ 3.9	$ 1.6	$ 3.0
Income Tax Benefit	1.1	0.5	0.9
Performance Shares
Share-Based Compensation Expense [Line Items]
Total Share-Based Compensation Expense	3.1	0.7	2.0
Restricted Stock Units
Share-Based Compensation Expense [Line Items]
Total Share-Based Compensation Expense	$ 0.8	$ 0.9	$ 1.0