Employee Share-Based Incentive Compensation Plans - Restricted Shares (Details) - Restricted Stock - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Restricted Shares
Beginning of period (in shares)	35,390	37,595	38,350
Vested (in shares)	(13,150)	(13,475)	(11,650)
Issued (in shares)	10,670	11,405	10,895
Forfeited (in shares)	0	(135)	0
End of period (in shares)	32,910	35,390	37,595
Unamortized Issue Date Fair Value
Beginning of period	$ 19.9	$ 16.2	$ 15.5
Vested	0.0	0.0	0.0
Issued	19.6	20.0	16.0
Forfeited	0.0	0.0	0.0
Expense recognized	(18.5)	(16.3)	(15.3)
End of period	$ 21.0	$ 19.9	$ 16.2