Accounting Policies - PPE (Details 6) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Property, plant and equipment [Line Items]
Allowance for Funds Used During Construction, Capitalized Interest	$ 2,640	$ 2,807	$ 2,290
Public Utilities, Allowance for Funds Used During Construction, Capitalized Cost of Equity	$ 1,270	$ 698	$ 1,897