Other Income, Net (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Other Income, net [Abstract]
AFUDC - Equity	$ 25.1	$ 20.1	$ 5.6
Gain on repurchase of notes	23.6	0.0	0.0
Gain on asset sales	19.6	22.9	7.5
Other, net	12.5	15.9	0.3
Other income, net	$ 80.8	$ 58.9	$ 13.4