Segment Information (Company's Segment Information, Continuing Operations) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Segment Reporting Information [Line Items]
Operating revenues	$ 699,275	$ 583,565
Operations and maintenance expense	142,581	125,075
Purchased gas	227,712	132,153
Depreciation and amortization	78,346	72,944
Taxes other than income taxes	23,007	21,041
Operating income	227,629	232,352
Interest expense, net	53,027	50,382
Allowance for funds used during construction	(5,839)	(2,934)
Other	(1,702)	(3,551)
Income before income taxes	182,143	188,455
Provision for income taxes	(17,233)	4,766
Net income	199,376	183,689
Capital expenditures	183,322	178,009
Total assets	14,877,023		$ 14,658,278
Water [Member] | Regulated [Member]
Segment Reporting Information [Line Items]
Operating revenues	239,198	228,353
Operations and maintenance expense	86,088	78,347
Depreciation and amortization	48,716	45,138
Taxes other than income taxes	15,891	15,421
Operating income	88,503	89,447
Interest expense, net	27,554	26,460
Allowance for funds used during construction	(5,149)	(3,247)
Other	(1,944)	(1,429)
Income before income taxes	68,042	67,663
Provision for income taxes	7,499	3,633
Net income	60,543	64,030
Capital expenditures	100,803	113,793
Total assets	8,487,684		8,403,586
Natural Gas [Member] | Regulated [Member]
Segment Reporting Information [Line Items]
Operating revenues	445,183	343,115
Operations and maintenance expense	59,452	51,326
Purchased gas	217,306	122,888
Depreciation and amortization	29,704	27,590
Taxes other than income taxes	6,191	4,447
Operating income	132,530	136,864
Interest expense, net	20,652	17,296
Allowance for funds used during construction	(690)	313
Other	(444)	(428)
Income before income taxes	113,012	119,683
Provision for income taxes	(26,474)	432
Net income	139,486	119,251
Capital expenditures	82,122	64,114
Total assets	6,090,675		5,960,602
Other [Member]
Segment Reporting Information [Line Items]
Operating revenues	14,894	12,097
Operations and maintenance expense	(2,959)	(4,598)
Purchased gas	10,406	9,265
Depreciation and amortization	(74)	216
Taxes other than income taxes	925	1,173
Operating income	6,596	6,041
Interest expense, net	4,821	6,626
Other	686	(1,694)
Income before income taxes	1,089	1,109
Provision for income taxes	1,742	701
Net income	(653)	408
Capital expenditures	397	$ 102
Total assets	$ 298,664		$ 294,090