Earnings Per Share - Reconciliation of Basic and Diluted Earnings Per Share Computations (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Earnings per common share:
Net income attributable to common stockholders	$ 470.6	$ 502.5	$ 556.8
Weighted average common shares outstanding (in shares)	19,303	20,533	21,493
Earnings per common share (in dollars per share)	$ 24.38	$ 24.47	$ 25.91
Earnings per common share - assuming dilution:
Net income attributable to common stockholders	$ 470.6	$ 502.5	$ 556.8
Weighted average common shares outstanding (in shares)	19,303	20,533	21,493
Common equivalent shares:
Share-based awards (in shares)	223	309	350
Weighted average common shares outstanding - assuming dilution (in shares)	19,526	20,842	21,843
Earnings per common share assuming dilution (in dollars per share)	$ 24.10	$ 24.11	$ 25.49