Pension and Post-Employment Benefits - Defined Benefit Pension Plan (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Plan net pension (credit)/charge:
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Interest Cost, Statement of Income or Comprehensive Income [Extensible Enumeration]	Other Nonoperating Income (Expense)	Other Nonoperating Income (Expense)	Other Nonoperating Income (Expense)
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Expected Return (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Other Nonoperating Income (Expense)	Other Nonoperating Income (Expense)	Other Nonoperating Income (Expense)
United Kingdom Plan [Member]
Plan assumptions at December 31, (%):
Discount rate	4.59%	4.91%	1.84%
Inflation rate	2.70%	2.85%	3.55%
Rate of return on plan assets - overall on bid-value	4.25%	4.00%	2.30%
Plan asset allocation by category (%):
Total plan asset allocation by category	100.00%	100.00%	100.00%
United Kingdom Plan [Member] | Cash [Member]
Plan asset allocation by category (%):
Total plan asset allocation by category	4.00%	4.00%	13.00%
United Kingdom Plan [Member] | Defined Benefit Plan Debt Securities And Insurance Contracts [Member]
Plan asset allocation by category (%):
Total plan asset allocation by category	96.00%	96.00%	82.00%
United Kingdom Plan [Member] | Defined Benefit Plan Equity Securities And Real Estate [Member]
Plan asset allocation by category (%):
Total plan asset allocation by category	0.00%	0.00%	5.00%
United Kingdom [Member]
Plan net pension (credit)/charge:
Service cost	$ 3.3
Interest cost on PBO	18.5
Expected return on plan assets	(25.7)
Amortization of prior service cost/(credit)	0.5
Amortization of actuarial net losses	0.0
United Kingdom [Member] | United Kingdom Plan [Member]
Plan net pension (credit)/charge:
Service cost	3.4	$ 2.2	$ 1.6
Interest cost on PBO	19.6	10.1	7.6
Expected return on plan assets	(25.2)	(16.0)	(15.5)
Amortization of prior service cost/(credit)	0.5	0.5	0.3
Amortization of actuarial net losses	(1.6)	0.0	1.6
Settlement event	0.0	0.0	(0.3)
Net periodic cost/(benefit)	$ (3.3)	$ (3.2)	$ (4.7)