Leases - Right-of-Use Assets and Lease Obligations (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Right-of-use assets under operating leases:
Other long-term assets	$ 540.3	$ 527.0
Lease obligations under operating leases:
Accrued liabilities	116.3	113.9
Other long-term liabilities	438.9	422.4
Lease obligations under operating leases	$ 555.2	$ 536.3
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	us-gaap:OtherAssetsNoncurrent	us-gaap:OtherAssetsNoncurrent
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	us-gaap:AccruedLiabilitiesCurrent	us-gaap:AccruedLiabilitiesCurrent
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	us-gaap:LongTermDebtAndCapitalLeaseObligations	us-gaap:LongTermDebtAndCapitalLeaseObligations