Income Taxes Income Taxes - Deferred Taxes By Balance Sheet Account (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Deferred income taxes - current assets	$ 0.0	$ 168.8
Deferred income taxes - long-term assets	309.5	65.3
Other current liabilities	0.0	(6.0)
Deferred income taxes - long-term liabilities	(300.6)	(1.9)
Net deferred tax asset	$ 8.9	$ 226.2