Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Income Tax Disclosure [Abstract]
Effective tax rate		87.20%	6.90%
U.S. federal statutory rate		35.00%	35.00%
Effective tax rate, excluding tax benefit realized from sale of regulatory asset			15.50%
Income tax benefit realized from sale of regulatory assets	$ 35.5		$ 35.5