Summary of Significant Accounting Policies Fuel Inventories (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Other	$ 81.8	$ 55.6
Public Utilities, Inventory, Fuel [Member]
Public Utilities, Inventory	82.4	$ 119.3
Other Assets	2.7		$ 11.0
Other	$ 3.0