Retirement Benefit Plans (Narrative) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Jul. 01, 2021
Defined Benefit Plan Disclosure [Line Items]
Expected long-term return on assets (as a percent)	5.50%
Shortfall amortization period	7 years
Funded status of plan				$ (0.5)
Employee annual contribution percent of eligible compensation	75.00%
Employer matching contribution, percent of match	100.00%
Employer matching contribution, percent of employees' gross pay	2.00%
Employer matching contribution, additional percent of match	50.00%
Employer additional matching contribution, percent of employees' gross pay	6.00%
Employer additional matching contribution, percent of employees' gross pay, default	3.00%
Compensation expense	$ 13.1	$ 13.8	$ 13.2
Fixed Income Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	64.50%
Defined Benefit Plan, Plan Assets, Actual Allocation, Percentage	63.60%
Equity Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	35.50%
Defined Benefit Plan, Plan Assets, Actual Allocation, Percentage	35.70%
Defined Benefit Plan, Cash and Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Actual Allocation, Percentage	0.70%