Treasury Stock Transactions (Details) - USD ($) shares in Millions, $ in Millions		3 Months Ended	12 Months Ended
		Mar. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Equity, Class of Treasury Stock
Number of Treasury Shares Repurchased			5.7	5.7	1.9
Cost of Shares Repurchased	[1]		$ 252.0	$ 200.1	$ 50.0
Commission Paid on Stock Repurchases			0.1
Share Repurchases Excise Tax			1.9	0.0	0.0
Accelerated Share Repurchase Agreement
Equity, Class of Treasury Stock
Cost of Shares Repurchased			50.0	$ 50.0	$ 50.0
Repurchase Program Authorized in December 2023
Equity, Class of Treasury Stock
Stock Repurchase Program, Authorized Amount			$ 500.0
Repurchase Program Authorized in December 2022
Equity, Class of Treasury Stock
Stock Repurchase Program Expiration Date			Dec. 31, 2023
Stock Repurchase Program, Authorized Amount			$ 250.0
Remaining Amount of Treasury Share Repurchases Authorized Under Stock Repurchase Program			$ 0.0
Repurchase Program Authorized in October 2021
Equity, Class of Treasury Stock
Stock Repurchase Program Expiration Date			Dec. 31, 2022
Stock Repurchase Program, Authorized Amount			$ 250.0
Remaining Amount of Treasury Share Repurchases Authorized Under Stock Repurchase Program			$ 0.0
Subsequent Event | Accelerated Share Repurchase Agreement
Equity, Class of Treasury Stock
Cost of Shares Repurchased		$ 100.0

[1] Includes $0.1 million of commissions for the years ended December 31, 2023 and 2022, respectively. There were no commissions for the year ended December 31, 2021. Also includes $1.9 million of excise tax for the year ended December 31, 2023. There were no excise taxes during the years ended December 31, 2022 and 2021.