Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Taxes [Line Items]
Effective Tax Rate	18.20%	69.20%
Federal Statutory Rate	21.00%		24.50%	35.00%
Reduction to Income Tax Expense Due to Remeasurement of Deferred Income Tax Assets and Liabilities	$ 5,000		$ 103,500
Reduction In Deferred Taxes for Rate Regulated Activities Due to Remeasurement of Deferred Income Tax Assets and Liabilities			336,700
Decrease to Recoverable Future Taxes Due to Change in Corporate Tax Rate			65,700
Increase in Taxes Refundable to Customers Due to Change in Corporate Tax Rate			271,000
Federal [Member] | Other Noncurrent Assets [Member]
Income Taxes [Line Items]
Income Taxes Receivable	$ 42,093		$ 0