Anticipated adjustment to expected benefit to (reduction of) Retained Earnings (Detail) - Revenue from Contracts with Customers [Member] - Retained Earnings [Member] - Approximation of Anticipated Impacts [Member] $ in Millions	Dec. 31, 2017 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Effect of Adoption Adjustments to retained earnings	$ 149.0
Other Adjustments [Member]
Summary Of Significant Accounting Policies [Line Items]
Effect of Adoption Adjustments to retained earnings	4.0
Capitalization of Work-In-Process [Member]
Summary Of Significant Accounting Policies [Line Items]
Effect of Adoption Adjustments to retained earnings	9.0
Increase in Tax Liability [Member]
Summary Of Significant Accounting Policies [Line Items]
Effect of Adoption Adjustments to retained earnings	45.0
MA [Member] | Recognition of Deferred Revenue [Member]
Summary Of Significant Accounting Policies [Line Items]
Effect of Adoption Adjustments to retained earnings	105.0
MA [Member] | Increase to capitalized sales commissions [Member]
Summary Of Significant Accounting Policies [Line Items]
Effect of Adoption Adjustments to retained earnings	$ 76.0