Consolidated Statements Of Operations And Comprehensive Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Consolidated Statements Of Net Income [Abstract]
Operating revenues	$ 255,585	$ 201,132
Operating expenses:
Operations and maintenance	106,637	79,314
Purchased gas	12,770
Depreciation	45,566	39,074
Amortization	679	336
Taxes other than income taxes	16,436	14,969
Total operating expenses	182,088	133,693
Operating income	73,497	67,439
Other expense (income):
Interest expense	35,122	27,869
Interest income	(5,035)	(19)
Allowance for funds used during construction	(2,948)	(4,056)
Change in fair value of interest rate swap agreements		34,782
Gain on sale of other assets	(105)	(220)
Equity loss (earnings) in joint venture	127	(543)
Other	1,679	872
Income before income taxes	44,657	8,754
Provision for income tax benefit	(7,124)	(8,170)
Net income	51,781	16,924
Comprehensive income	$ 51,781	$ 16,924
Net income per common share:
Basic	$ 0.22	$ 0.09
Diluted	$ 0.20	$ 0.09
Average common shares outstanding during the period:
Basic	236,122	178,213
Diluted	255,054	178,552