Segment Information (Company's Segment Information, Continuing Operations) (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2022	Mar. 31, 2022	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Segment Reporting Information [Line Items]
Operating revenues	$ 448,756		$ 397,032		$ 1,148,031	$ 980,597
Operations and maintenance expense	134,981		127,515		277,562	252,590
Purchased gas	75,143		44,897		302,855	177,050
Depreciation and amortization	79,176		74,172		157,522	147,116
Taxes other than income taxes	21,720		21,120		44,727	42,161
Operating income	137,736		129,328		365,365	361,680
Interest expense, net	54,397		51,698		107,424	102,080
Allowance for funds used during construction	(6,151)		(4,906)		(11,990)	(7,840)
Other	(901)		(2,164)		(2,603)	(5,715)
Income before income taxes	90,391		84,700		272,534	273,155
Provision for income taxes	8,100		3,786		(9,133)	8,552
Net income	82,291	$ 199,376	80,914	$ 183,689	281,667	264,603
Capital expenditures					424,645	404,557
Total assets	15,046,164				15,046,164		$ 14,658,278
Water [Member] | Regulated [Member]
Segment Reporting Information [Line Items]
Operating revenues	269,355		248,177		508,553	476,530
Operations and maintenance expense	92,815		77,801		178,903	156,148
Depreciation and amortization	50,260		45,546		98,976	90,684
Taxes other than income taxes	15,562		16,044		31,453	31,465
Operating income	110,718		108,786		199,221	198,233
Interest expense, net	27,604		27,122		55,159	53,582
Allowance for funds used during construction	(5,347)		(4,438)		(10,496)	(7,685)
Other	(1,728)		(1,940)		(3,673)	(3,369)
Income before income taxes	90,189		88,042		158,231	155,705
Provision for income taxes	13,847		9,193		21,346	12,826
Net income	76,342		78,849		136,885	142,879
Capital expenditures					216,612	247,911
Total assets	8,645,314				8,645,314		8,403,586
Natural Gas [Member] | Regulated [Member]
Segment Reporting Information [Line Items]
Operating revenues	167,729		141,562		612,912	484,677
Operations and maintenance expense	44,907		52,334		104,359	103,660
Purchased gas	63,392		39,788		280,698	162,676
Depreciation and amortization	29,131		28,121		58,835	55,711
Taxes other than income taxes	5,614		4,638		11,805	9,085
Operating income	24,685		16,681		157,215	153,545
Interest expense, net	19,171		20,422		39,823	37,719
Allowance for funds used during construction	(804)		(468)		(1,493)	(155)
Other	10		(439)		(434)	(867)
Income before income taxes	6,308		(2,834)		119,319	116,848
Provision for income taxes	(5,170)		(4,739)		(31,645)	(4,307)
Net income	11,478		1,905		150,964	121,155
Capital expenditures					207,394	156,252
Total assets	6,121,964				6,121,964		5,960,602
Other [Member]
Segment Reporting Information [Line Items]
Operating revenues	11,672		7,293		26,566	19,390
Operations and maintenance expense	(2,741)		(2,620)		(5,700)	(7,218)
Purchased gas	11,751		5,109		22,157	14,374
Depreciation and amortization	(215)		505		(289)	721
Taxes other than income taxes	544		438		1,469	1,611
Operating income	2,333		3,861		8,929	9,902
Interest expense, net	7,622		4,154		12,442	10,779
Allowance for funds used during construction					(1)
Other	817		215		1,504	(1,479)
Income before income taxes	(6,106)		(508)		(5,016)	602
Provision for income taxes	(577)		(668)		1,166	33
Net income	(5,529)		$ 160		(6,182)	569
Capital expenditures					639	$ 394
Total assets	$ 278,886				$ 278,886		$ 294,090