Goodwill And Other Acquired Intangible Assets - Estimated Future Amortization Expense for Acquired Intangible Assets Subject to Amortization (Detail) $ in Millions	Mar. 31, 2019 USD ($)
Estimated Future Amortization Expense for Acquired Intangible Assets Subject to Amortization [Abstract]
2019 (After March 31)	$ 71.0
2020	100.5
2021	100.3
2022	100.3
2023	97.3
Thereafter	1,061.0
Total estimated future amortization	$ 1,530.4