Consolidated Statements Of Operations And Comprehensive Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Consolidated Statements Of Operations And Comprehensive Income [Abstract]
Operating revenues	$ 348,647	$ 243,626	$ 988,700	$ 663,650
Operating expenses:
Operations and maintenance	136,174	82,022	371,415	247,781
Purchased gas	16,744		72,934
Depreciation	68,175	39,489	181,666	118,113
Amortization	1,766	444	4,412	(2,140)
Taxes other than income taxes	20,555	15,201	56,424	45,038
Total operating expenses	243,414	137,156	686,851	408,792
Operating income	105,233	106,470	301,849	254,858
Other expense (income):
Interest expense	49,861	32,643	136,650	92,239
Interest income	(114)	(9,680)	(5,346)	(18,117)
Allowance for funds used during construction	(3,543)	(4,613)	(8,721)	(12,280)
Change in fair value of interest rate swap agreements				23,742
Loss on debt extinguishment				18,920
Gain on sale of other assets	(233)	(175)	(358)	(443)
Equity loss (earnings) in joint venture	3,626	(135)	3,283	(1,918)
Other	(4,127)	1,494	(3,170)	4,293
Income before income taxes	59,763	86,936	179,511	148,422
Provision for income taxes (benefit)	4,031	(1,553)	(2,631)	(11,894)
Net income	55,732	88,489	182,142	160,316
Comprehensive income	$ 55,732	$ 88,489	$ 182,142	$ 160,316
Net income per common share:
Basic	$ 0.22	$ 0.38	$ 0.73	$ 0.76
Diluted	$ 0.22	$ 0.38	$ 0.71	$ 0.76
Average common shares outstanding during the period:
Basic	254,280	232,053	248,212	209,971
Diluted	255,162	232,464	255,139	210,335