Leases - Schedule of Information on Leases (Detail) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019	Jan. 01, 2019
Leases [Abstract]
Lease cost	$ 19.0	$ 56.0
Cash paid for leases recognized in operating cash flows	16.9	54.1
Right-of-use assets obtained in exchange for new lease liabilities	16.4	32.8
Right-of-use asset	$ 259.3	$ 259.3	$ 274.7
Operating Lease Right Of Use Asset Statement Of Financial Position Extensible List	us-gaap:OtherAssets	us-gaap:OtherAssets	us-gaap:OtherAssetsNoncurrent
Lease liabilities, current	$ 61.8	$ 61.8	$ 62.2
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	us-gaap:OtherLiabilitiesCurrent	us-gaap:OtherLiabilitiesCurrent	us-gaap:OtherLiabilitiesCurrent
Lease liabilities, noncurrent	$ 209.1	$ 209.1	$ 221.2
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	us-gaap:OtherLiabilitiesNoncurrent	us-gaap:OtherLiabilitiesNoncurrent	us-gaap:OtherLiabilitiesNoncurrent
Weighted-average remaining lease term	6 years 3 months 18 days	6 years 3 months 18 days
Weighted-average discount rate	2.80%	2.80%