Income Taxes (Details) - USD ($)		6 Months Ended
		Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Income Tax Examination [Line Items]
Net Deferred Tax Liability associated with the Unrecognized Tax Benefit Amounts and Related NOLs and Tax Credit Carryforwards		$ (1,100,000)		$ (1,100,000)
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent		21.00%	21.00%
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent		6.20%	6.20%
Effective Income Tax Rate Reconciliation, Prior Year Income Taxes, Percent		2.20%	0.00%
Effective Income Tax Rate Reconciliation, Other Regulatory Items, Percent	[1]	(0.50%)	(1.70%)
Regulatory difference - reversal of prior quarters' ARAM deferral (b)		(1.00%)	(0.90%)
Effective Income Tax Rate Reconciliation, Other Adjustments, Percent		0.30%	0.50%
Effective Income Tax Rate Reconciliation, Percent		28.20%	25.10%
Unrecognized Tax Benefits [Abstract]
Unrecognized tax benefit — Permanent tax positions		$ 2,100,000		2,000,000.0
Unrecognized tax benefit — Temporary tax positions		800,000		800,000
Total unrecognized tax benefit		2,900,000		2,800,000
NOL and tax credit carryforwards		(2,000,000.0)		(2,100,000)
Upper bound of decrease in unrecognized tax benefit that is reasonably possible		2,200,000
Amounts accrued for penalties related to unrecognized tax benefits		0		$ 0
Internal Revenue Service (IRS)
Tax Audits [Abstract]
Potential Tax Adjustments		0
State Jurisdiction (Wisconsin)
Tax Audits [Abstract]
Potential Tax Adjustments		$ 0

[1] Regulatory differences for income tax primarily relate to the flow back of excess deferred taxes to customers through the average rate assumption method and the impact of allowance for funds used during construction - equity. Year-to-date variations primarily relates to the impact of allowance for funds used during construction - equity.