Goodwill and Other Intangibles - Other Intangible Assets and Capitalized Software (Detail) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 210.0	$ 221.3
Less: Accumulated Amortization	106.2	108.7
Net Book Value	103.8	112.6
Computer Software
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	4,404.8	4,337.4
Less: Accumulated Amortization	2,810.5	2,744.5
Net Book Value	$ 1,594.3	$ 1,592.9