Goodwill and Other Intangibles - Narrative (Detail) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Jun. 30, 2021	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill		$ 706.2	$ 707.2	$ 696.8
Amortization of intangible assets		14.8	16.9	16.6
Other Intangible Assets
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets		14.8	16.9	16.6
Estimated future amortization expense for 2022		9.9
Estimated future amortization expense for 2023		9.6
Estimated future amortization expense for 2024		9.5
Estimated future amortization expense for 2025		8.9
Estimated future amortization expense for 2026		8.6
Computer Software
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets		$ 390.1	$ 366.9	$ 339.1
Parilux Investment Technology, LLC
Acquired Finite-Lived Intangible Assets [Line Items]
Purchase price	$ 17.6
Goodwill	4.2
Intangible assets acquired	$ 13.4