Derivative Instruments And Hedging Activities - Gains (Losses) Recognized in AOCI and Reclassified from AOCI on Derivatives (Effective Portion) (Detail) - Accounting Standards Update 2018-02 - USD ($) $ in Millions	Sep. 30, 2019	Jan. 01, 2019
Derivative Instruments, Gain (Loss) [Line Items]
Effect of adoption adjustment reduction to retained earnings		$ 0.0
Retained Earnings
Derivative Instruments, Gain (Loss) [Line Items]
Effect of adoption adjustment reduction to retained earnings		19.8
Retained Earnings | Net Investment Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Effect of adoption adjustment reduction to retained earnings	$ 2.5
Accumulated Other Comprehensive Loss
Derivative Instruments, Gain (Loss) [Line Items]
Effect of adoption adjustment reduction to retained earnings		$ (19.8)
Accumulated Other Comprehensive Loss | Net Investment Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Effect of adoption adjustment reduction to retained earnings	$ (2.5)