Employee Benefit Plans (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
U.S.
Defined Contribution Plan Disclosure [Line Items]
Employer contributions to plan	$ 17.4	$ 15.2	$ 11.6
United Kingdom
Defined Contribution Plan Disclosure [Line Items]
Employer contributions to plan	$ 7.3	$ 7.7	$ 6.4