Segment Information (Company's Segment Information, Continuing Operations) (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting Information [Line Items]
Operating revenues	$ 348,647			$ 243,626			$ 988,700	$ 663,650
Operations and maintenance expense	136,174			82,022			371,415	247,781
Purchased gas	16,744						72,934
Depreciation and amortization	69,941			39,933			186,078	115,973
Operating income (loss)	105,233			106,470			301,849	254,858
Interest expense, net	49,747			22,963			131,304	74,122
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
Equity earnings in joint venture	(3,626)			135			(3,283)	1,918
Provision for income taxes	4,031			(1,553)			(2,631)	(11,894)
Net income (loss)	55,732	$ 74,629	$ 51,781	88,489	$ 54,903	$ 16,924	182,142	160,316
Capital expenditures							554,141	401,558
Water [Member] | Regulated [Member]
Segment Reporting Information [Line Items]
Operating revenues	255,725			242,856			706,008	661,082
Operations and maintenance expense	79,313			81,078			229,652	229,498
Depreciation and amortization	42,955			39,781			127,214	115,454
Operating income (loss)	117,551			106,833			303,850	272,596
Interest expense, net	27,063			24,408			78,500	72,133
Allowance for funds used during construction	3,082			4,613			7,905	12,280
Provision for income taxes	8,081			(2,561)			18,402	291
Net income (loss)	85,379			88,888			214,376	210,285
Capital expenditures							376,064	401,558
Natural Gas [Member] | Regulated [Member]
Segment Reporting Information [Line Items]
Operating revenues	88,880						273,798
Operations and maintenance expense	59,560						120,192
Purchased gas	14,841						68,807
Depreciation and amortization	25,793						56,026
Operating income (loss)	(15,459)						19,974
Interest expense, net	9,333						21,260
Allowance for funds used during construction	461						816
Provision for income taxes	(1,219)						(8,131)
Net income (loss)	(22,351)						9,177
Capital expenditures							134,632
Other [Member]
Segment Reporting Information [Line Items]
Operating revenues	4,042			770			8,894	2,568
Operations and maintenance expense	(2,699)			944			21,571	18,283
Purchased gas	1,903						4,127
Depreciation and amortization	1,193			152			2,838	519
Operating income (loss)	3,141			(363)			(21,975)	(17,738)
Interest expense, net	13,351			(1,445)			31,544	1,989
Allowance for funds used during construction
Change in fair value of interest rate swap agreements								23,742
Equity earnings in joint venture	(3,626)			135			(3,283)	1,918
Provision for income taxes	(2,831)			1,008			(12,902)	(12,185)
Net income (loss)	$ (7,296)			$ (399)			(41,411)	(49,969)
Capital expenditures							$ 43,445