Summary of Significant Accounting Policies Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Noncash Investing and Financing Items [Abstract]
Change in capital expenditure accrual balance	$ 8.8	$ (57.4)	$ 60.2
Other Noncash Income (Expense) [Abstract]
Right-of-use assets obtained in exchange for operating lease obligations	16.6	0.0	0.0
Supplemental Cash Flow Information [Abstract]
Cash paid for interest, net of capitalized interest	126.9	136.9	134.9
Cash paid (refund received) for income taxes, net	(66.7)	0.8	(0.3)
Cash paid for amounts included in the measurement of lease liabilities	$ 25.3	$ 0.0	$ 0.0