Employee Share-Based Incentive Compensation Plans - Performance Shares (Details) - USD ($) $ in Millions	1 Months Ended		3 Months Ended		9 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Target Performance Shares Outstanding
Beginning of period (in shares)			32,392	34,992	34,859	37,031
Shares paid or expired (in shares)			0	0	(13,150)	(13,475)
New grants (in shares)			25	0	10,670	11,405
Forfeitures and cancellations (in shares)			(1)	(133)	37	(102)
End of period (in shares)			32,416	34,859	32,416	34,859
Accrued Expense
Beginning of period			$ 29.8	$ 52.0	$ 71.1	$ 69.4
Shares paid or expired			0.0	0.0	(48.7)	(44.9)
New grants			0.0	0.0	0.0	0.0
Forfeitures and cancellations			(0.3)	0.0	0.3	0.3
Expense recognized			22.5	3.7	29.3	30.9
End of period			$ 52.0	$ 55.7	$ 52.0	$ 55.7
Performance Share
Accrued Expense
Percentage of target payout - minimum actual	200.00%	188.00%