Significant Accounting Policies Schedule of New Accounting Pronouncements (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
New Accounting Pronouncements or Change in Accounting Principle
Short-term Debt	$ 0.0	$ 352.0
Long-term Debt	2,999.4	2,449.4
Other Assets	$ 617.3	637.4
Previously Reported
New Accounting Pronouncements or Change in Accounting Principle
Short-term Debt		352.4
Long-term Debt		2,475.1
Other Assets		663.5
Accounting Standards Update 2015-03 | Restatement Adjustment
New Accounting Pronouncements or Change in Accounting Principle
Short-term Debt		(0.4)
Long-term Debt		(25.7)
Other Assets		$ (26.1)