Leases - Schedule of Information on Leases (Detail) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019	Jan. 01, 2019
Leases [Abstract]
Lease cost	$ 18.4	$ 37.0
Cash paid for leases recognized in operating cash flows	18.4	37.2
Right-of-use assets obtained in exchange for new lease liabilities	10.6	16.4
Right-of-use asset	$ 257.6	$ 257.6	$ 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	$ 62.5	$ 62.5	$ 62.2
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	us-gaap:OtherLiabilitiesCurrent	us-gaap:OtherLiabilitiesCurrent	us-gaap:OtherLiabilitiesCurrent
Lease liabilities, noncurrent	$ 205.4	$ 205.4	$ 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 2 months 12 days	6 years 2 months 12 days
Weighted-average discount rate	2.70%	2.70%