Description of Business and Basis of Presentation - Adjustment to Retained Earnings (Detail) - New Revenue Accounting Standard [Member] - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
New Accounting Pronouncement or Change in Accounting Principle, Retrospective Adjustments [Abstract]
Effect of Adoption Adjustments to Retained Earnings		$ (156.1)
Retained Earnings [Member]
New Accounting Pronouncement or Change in Accounting Principle, Retrospective Adjustments [Abstract]
Effect of Adoption Adjustments to Retained Earnings	$ 156.0	$ (156.1)
Retained Earnings [Member] | Other Adjustments [Member] | Various Assets [Member]
New Accounting Pronouncement or Change in Accounting Principle, Retrospective Adjustments [Abstract]
Effect of Adoption Adjustments to Retained Earnings	4.0
Retained Earnings [Member] | Capitalization of Work-In-Process [Member] | Other Current Assets [Member]
New Accounting Pronouncement or Change in Accounting Principle, Retrospective Adjustments [Abstract]
Effect of Adoption Adjustments to Retained Earnings	9.0
Retained Earnings [Member] | Increase in Tax Liability [Member] | Deferred Tax Liabilities [Member]
New Accounting Pronouncement or Change in Accounting Principle, Retrospective Adjustments [Abstract]
Effect of Adoption Adjustments to Retained Earnings	(43.0)
MA [Member] | Retained Earnings [Member] | Increase to capitalized sales commissions [Member] | Other current assets, Other assets, Accounts Payable and Accrued Liabilities [Member]
New Accounting Pronouncement or Change in Accounting Principle, Retrospective Adjustments [Abstract]
Effect of Adoption Adjustments to Retained Earnings	78.0
MA [Member] | Retained Earnings [Member] | Recognition of Deferred Revenue or Increase in Unbilled Receivables [Member] | Deferred Revenue Accounts Receivable and Other Assets [Member]
New Accounting Pronouncement or Change in Accounting Principle, Retrospective Adjustments [Abstract]
Effect of Adoption Adjustments to Retained Earnings	$ 108.0