Segment Information (Company's Segment Information, Continuing Operations) (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Segment Reporting Information [Line Items]
Operating revenues	$ 384,468		$ 218,892		$ 640,053	$ 420,024
Operations and maintenance expense	128,604		86,445		235,241	165,759
Purchased gas	43,420				56,190
Depreciation and amortization	69,892		36,630		116,137	76,040
Operating income (loss)	123,119		80,949		196,616	148,388
Interest expense, net	51,470		23,309		81,557	51,159
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
Equity earnings in joint venture	470		1,240		343	1,783
Provision for income taxes	462		(2,171)		(6,662)	(10,341)
Net income (loss)	74,629	$ 51,781	54,903	$ 16,924	126,410	71,827
Capital expenditures					293,090	269,171
Water [Member] | Regulated [Member]
Segment Reporting Information [Line Items]
Operating revenues	234,086		218,006		450,283	418,226
Operations and maintenance expense	76,645		74,082		150,339	148,420
Depreciation and amortization	42,748		36,412		84,259	75,671
Operating income (loss)	99,794		93,112		186,300	165,765
Interest expense, net	25,970		24,067		51,505	47,725
Allowance for funds used during construction	1,911		3,611		4,823	7,667
Provision for income taxes	7,194		1,780		10,321	2,731
Net income (loss)	68,995		69,579		128,929	121,520
Capital expenditures					217,373	269,171
Natural Gas [Member] | Regulated [Member]
Segment Reporting Information [Line Items]
Operating revenues	146,880				184,915
Operations and maintenance expense	50,876				59,533
Purchased gas	41,593				53,966
Depreciation and amortization	25,727				30,234
Operating income (loss)	24,693				36,530
Interest expense, net	9,334				11,926
Allowance for funds used during construction	319				355
Provision for income taxes	(2,399)				(5,820)
Net income (loss)	17,999				31,535
Capital expenditures					75,458
Other [Member]
Segment Reporting Information [Line Items]
Operating revenues	3,502		886		4,855	1,798
Operations and maintenance expense	1,083		12,363		25,369	17,339
Purchased gas	1,827				2,224
Depreciation and amortization	1,417		218		1,644	369
Operating income (loss)	(1,368)		(12,163)		(26,214)	(17,377)
Interest expense, net	16,166		(758)		18,126	3,434
Allowance for funds used during construction
Change in fair value of interest rate swap agreements			(11,040)			23,742
Equity earnings in joint venture	470		1,240		343	1,783
Provision for income taxes	(4,333)		(3,951)		(11,163)	(13,072)
Net income (loss)	$ (12,365)		$ (14,676)		(34,054)	(49,693)
Capital expenditures					$ 259