Summary of Significant Accounting Policies Cash and Cash Equivalents (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Supplemental Cash Flow Information [Line Items]
Unrestricted Cash	$ 443.8	$ 376.1
Restricted cash	21.6	18.1
Supplemental Disclosures
Cash paid for interest, net of capitalized interest	139.1	139.4	$ 163.2
Cash paid (refund received) for income taxes, net	(123.5)	487.8	0.3
Non-cash investing activities
Change in capital expenditure accrual balance	$ (32.8)	$ (129.2)	$ 8.4