Acquisitions - Additional Information (Detail) - USD ($) $ in Millions		3 Months Ended
	Mar. 31, 2021	Mar. 31, 2021	Mar. 31, 2020
Business Acquisition [Line Items]
Revenues		$ 1,233.4	$ 1,173.6
Capita Life Pensions Services Limited [Member]
Business Acquisition [Line Items]
Business acquisition, effective date of acquisition	Mar. 01, 2021
Consideration paid, net of cash plus the costs of transaction	$ 7.1
Revenues		$ 3.7