Regulation and Rates (Details) - Subsidiaries [Member] - Purchased Gas Adjustment [Member] - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
Regulation and Rates [Line Items]
Purchased natural gas costs	$ 169,697	$ 406,162
Purchased natural gas costs, recoverable	(217,916)	(289,876)
Purchased natural gas adjustment, interest	$ 2,385	$ 6,558