Leases - Right-of-Use Assets and Lease Obligations (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Right-of-use assets under operating leases:
Other long-term assets	$ 527.0
Lease obligations under operating leases:
Accrued liabilities	113.9	$ 0.0
Other long-term liabilities	422.4
Lease obligations under operating leases	$ 536.3