Earnings Per Share - Calculations of Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions		12 Months Ended
		Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Disclosure Earnings Per Share Calculations Of Basic And Diluted Earnings Per Share [Abstract]
Income (Loss) from Continuing Operations, Per Basic Share		$ 6.00	$ 5.28	$ 4.75
Calculation of Basic Earnings Per Share:
Net Income		$ 140.3	$ 118.6	$ 87.2
Weighted shares outstanding - Basic (in shares)	[1]	23,389	22,469	18,371
Basic Earnings Per Share (in usd per share)		$ 6.00	$ 5.28	$ 4.75
Calculation of Diluted Earnings Per Share:
Net Income		$ 140.3	$ 118.6	$ 87.2
Reconciliation of Denominator:
Weighted shares outstanding - Basic (in shares)	[1]	23,389	22,469	18,371
Share-based Compensation		99	62	64
Adjusted denominator — Diluted	[1]	23,488	22,531	18,435
Income (Loss) from Continuing Operations, Per Diluted Share		$ 5.97	$ 5.26	$ 4.73
Diluted (in usd per share)		$ 5.97	$ 5.26	$ 4.73

[1] ) Weighted average shares reflect the impact of 4.4 million common shares issued in November 2023 in connection with the acquisition of FCG. See Notes 4 and 14 for additional details on the acquisition and related equity offering.