Income Taxes (Details)		9 Months Ended
		Sep. 30, 2019	Sep. 30, 2018
Income Tax Disclosure [Abstract]
Federal statutory rate		21.00%	21.00%
State tax (net of federal tax effect)		3.70%	3.70%
Wind PTCs		(7.70%)	0.00%
Plant regulatory differences	[1]	(3.60%)	(3.10%)
Other tax credits and tax credit and NOL allowances (net)		(1.30%)	(0.70%)
Other (net)		(0.60%)	(1.00%)
Effective income tax rate		11.50%	19.90%

[1] Regulatory differences for income tax primarily relate to the credit of excess deferred taxes to customers through the average rate assumption method and the timing of regulatory decisions regarding the return of excess deferred taxes. Income tax benefits associated with the credit of excess deferred credits are offset by corresponding revenue reductions and additional prepaid pension asset amortization.