Income Taxes (Details)	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Income Tax Disclosure [Abstract]
Federal statutory rate, percent	21.00%	21.00%
State tax (net of federal tax effect), percent	2.20%	2.30%
Plant regulatory differences, percent	(4.70%)	(3.80%)
Prior period adjustments, percent	(3.90%)	0.00%
Other tax credits, percent	(0.60%)	(0.70%)
Wind PTCs, percent	(0.50%)	(1.80%)
Other (net), percent	(0.50%)	0.00%
Effective income tax rate, percent	13.00%	17.00%