Consolidated Statements Of Operations And Comprehensive Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Consolidated Statements Of Operations And Comprehensive Income [Abstract]
Operating revenues	$ 384,468	$ 218,892	$ 640,053	$ 420,024
Operating expenses:
Operations and maintenance	128,604	86,445	235,241	165,759
Purchased gas	43,420		56,190
Depreciation	67,925	39,550	113,491	78,624
Amortization	1,967	(2,920)	2,646	(2,584)
Taxes other than income taxes	19,433	14,868	35,869	29,837
Total operating expenses	261,349	137,943	443,437	271,636
Operating income	123,119	80,949	196,616	148,388
Other expense (income):
Interest expense	51,666	31,727	86,788	59,596
Interest income	(196)	(8,418)	(5,231)	(8,437)
Allowance for funds used during construction	(2,230)	(3,611)	(5,178)	(7,667)
Change in fair value of interest rate swap agreements		(11,040)		23,742
Loss on debt extinguishment		18,935		18,935
Gain on sale of other assets	(20)	(48)	(125)	(268)
Equity earnings in joint venture	(470)	(1,240)	(343)	(1,783)
Other	(722)	1,912	957	2,784
Income before income taxes	75,091	52,732	119,748	61,486
Provision for income taxes (benefit)	462	(2,171)	(6,662)	(10,341)
Net income	74,629	54,903	126,410	71,827
Comprehensive income	$ 74,629	$ 54,903	$ 126,410	$ 71,827
Net income per common share:
Basic	$ 0.29	$ 0.25	$ 0.52	$ 0.36
Diluted	$ 0.29	$ 0.25	$ 0.50	$ 0.36
Average common shares outstanding during the period:
Basic	254,167	219,055	245,144	198,747
Diluted	254,434	219,790	254,452	199,303