Debt - Summary (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Debt
Total	$ 1,276.4	$ 1,151.4
Less: unamortized discount and debt issuance costs	(9.1)	(9.2)
Less: amounts due within one year	(399.5)	(0.3)
Total long-term debt	867.8	1,141.9
Unsecured revolving credit facility maturing September 10, 2029
Debt
Total	125.0	0.0
Senior unsecured notes, interest payable semi-annually at 1.30%, effective rate of 1.53%, maturing August 15, 2025
Debt
Total	$ 400.0	$ 400.0
Semi-annual rate (as a percent)	1.30%	1.30%
Effective rate (as a percent)	1.53%	1.53%
Senior unsecured notes, interest payable semi-annually at 2.15%, effective rate of 2.27%, maturing August 15, 2030
Debt
Total	$ 500.0	$ 500.0
Semi-annual rate (as a percent)	2.15%	2.15%
Effective rate (as a percent)	2.27%	2.27%
Senior unsecured notes, interest payable semi-annually at 6.85%, effective rate of 6.91%, maturing November 15, 2036
Debt
Total	$ 250.0	$ 250.0
Semi-annual rate (as a percent)	6.85%	6.85%
Effective rate (as a percent)	6.91%	6.91%
Other notes
Debt
Total	$ 1.4	$ 1.4