Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Income Tax Disclosure [Abstract]
Effective tax rate		64.10%	(2.70%)
U.S. federal statutory rate		35.00%	35.00%
Effective tax rate, excluding tax benefit realized from sale of regulatory asset			10.50%
Income tax benefit realized from sale of regulatory assets	$ 35.7		$ 35.7
Deferred tax asset, remaining amortization period		32 years