Income Taxes State Audits (Details) - USD ($)	6 Months Ended
	Jun. 30, 2021	Dec. 31, 2020
Income Tax Examination [Line Items]
Potential Tax Adjustments	$ 0
Unrecognized Tax Benefits, Income Tax Penalties Accrued	0	$ 0
WISCONSIN
Income Tax Examination [Line Items]
Potential Tax Adjustments	0
NSP-Minnesota
Income Tax Examination [Line Items]
Potential Tax Adjustments	$ 0