Debt Schedule of Interest Charges (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Debt Disclosure [Abstract]
Interest incurred	$ 272.2	$ 121.1	$ 147.7
Interest capitalized	(0.6)	(0.8)	2.7
Interest expensed	$ 271.6	$ 120.3	$ 145.0