Employee Benefit Plans Net Periodic Benefit Cost (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
U.S. Pension Plan | Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans
Service Cost	$ 2.0	$ 2.3	$ 3.8	$ 4.7
Interest Cost	16.4	21.4	32.8	42.8
Expected Return on Plan Assets	(16.7)	(21.8)	(33.4)	(43.6)
Amortization of Net Actuarial (Gain) Loss	2.1	3.7	4.3	7.4
Amortization of Prior Service Credit			0.0	0.0
Net Periodic Benefit Cost (Credit)	3.8	5.6	7.5	11.3
U.K. Pension Plan | Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans
Service Cost	0.0	0.0	0.0	0.0
Interest Cost	2.2	2.2	4.4	4.3
Expected Return on Plan Assets	(2.5)	(2.2)	(5.0)	(4.4)
Amortization of Net Actuarial (Gain) Loss	0.7	0.7	1.4	1.4
Amortization of Prior Service Credit			0.0	0.0
Net Periodic Benefit Cost (Credit)	0.4	0.7	0.8	1.3
Other Postretirement Benefit Plan | Other Postretirement Benefit Plans
Defined Benefit Plans and Other Postretirement Benefit Plans
Service Cost	0.0	0.0	0.0	0.0
Interest Cost	0.9	1.0	1.8	2.0
Expected Return on Plan Assets	(0.1)	(0.1)	(0.2)	(0.2)
Amortization of Net Actuarial (Gain) Loss	(0.3)	(0.3)	(0.5)	(0.6)
Amortization of Prior Service Credit			(0.1)	(0.1)
Net Periodic Benefit Cost (Credit)	$ 0.5	$ 0.6	$ 1.0	$ 1.1