Supplemental Cash Flow Information - Schedule of Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Supplemental Cash Flow Elements [Abstract]
Interest paid	$ 35.9	$ 17.7
Non-cash investing and financing activities (included in Accounts payable):
Unpaid purchases of property and equipment	10.1	3.5
Supplemental lease disclosures:
Operating lease liabilities arising from obtaining operating lease assets	24.3	4.9
Cash paid for amounts included in the measurement of operating lease liabilities	5.7	3.4
Finance lease liabilities arising from obtaining finance lease assets	2.1	2.2
Components of cash, cash equivalents and restricted cash:
Cash and cash equivalents	295.7	750.1	$ 780.3
Restricted cash included in Other assets	13.8	14.0
Total cash, cash equivalents and restricted cash presented on our Statements of Consolidated Cash Flows	$ 309.5	$ 764.1	$ 794.3	$ 278.6