Summary of Significant Accounting Policies Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Noncash Investing and Financing Items [Abstract]
Capital expenditure accrual balance	$ 37.8	$ 63.3	$ 54.5
Other Noncash Income (Expense) [Abstract]
Right-of-use assets obtained in exchange for operating lease obligations	11.0	16.6	0.0
Supplemental Cash Flow Information [Abstract]
Cash paid for interest, net of capitalized interest	118.4	126.9	136.9
Cash paid (refund received) for income taxes, net	(164.0)	(66.7)	0.8
Cash paid for amounts included in the measurement of lease liabilities	$ 25.7	$ 25.3	$ 0.0