Operations and Significant Accounting Policies - Non-Controlling Interest (Details) $ in Millions			3 Months Ended
	Apr. 29, 2020 USD ($)	Apr. 16, 2020 MW	Mar. 31, 2020 MW
Subsequent Event [Member]
Non-Controlling Interest Details [Line Items]
Proceeds from Noncontrolling Interests | $	$ 70
Glen Ullin Energy Center [Member]
Non-Controlling Interest Details [Line Items]
Generating Capacity Subject to Tax Equity Financing			106
South Peak [Member] | Subsequent Event [Member]
Non-Controlling Interest Details [Line Items]
Generating Capacity Subject to Tax Equity Financing		80