Goodwill and Other Intangibles - Other Intangible Assets and Capitalized Software (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Other Intangible Assets
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 221.3	$ 207.2
Less: Accumulated Amortization	108.7	86.6
Net Book Value	112.6	120.6
Computer Software
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	4,337.4	3,885.2
Less: Accumulated Amortization	2,744.5	2,377.9
Net Book Value	$ 1,592.9	$ 1,507.3