Reconciliation of Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Schedule Of Computation Of Basic And Diluted Earnings Per Common Share [Line Items]
Earnings Available to Common Shareholders	$ 36.1	$ 32.2	$ 44.2
Weighted Average Common Shares Outstanding—Basic	15,373	14,951	14,894
Plus: Diluted Effect of Incremental Shares	3	1	6
Weighted Average Common Shares Outstanding—Diluted	15,376	14,952	14,900
Earnings per Share—Basic and Diluted	$ 2.35	$ 2.15	$ 2.97