Washington Commission Tax Deferral Filing (Details) - USD ($) $ in Thousands		12 Months Ended
	May 01, 2018	Dec. 31, 2019	Apr. 30, 2019	Dec. 31, 2018	Dec. 31, 2017
Regulatory Assets [Line Items]
Income tax (benefit) expense		$ 17,073		$ 30,092	$ 255,143
Subsidiaries [Member]
Regulatory Assets [Line Items]
Income tax (benefit) expense	$ 34,600	$ 39,148		$ 50,700	$ 211,986
Subsidiaries [Member] | Electricity, US Regulated [Member] | Tax Cuts and Jobs Act [Member]
Regulatory Assets [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amended, Percentage			(3.40%)
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount			$ (72,900)
Subsidiaries [Member] | Natural Gas, US Regulated [Member] | Tax Cuts and Jobs Act [Member]
Regulatory Assets [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amended, Percentage			(2.70%)
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount			$ (23,600)