Segment Information (Company's Segment Information, Continuing Operations) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Segment Reporting Information [Line Items]
Operating revenues	$ 255,585	$ 201,132
Operations and maintenance expense	106,637	79,314
Purchased gas	12,770
Depreciation and amortization	46,245	39,410
Total taxes other than income	16,436	14,969
Operating income (loss)	73,497	67,439
Interest expense, net	30,087	27,850
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
Equity earnings in joint venture	(127)	543
Provision for income taxes	(7,124)	(8,170)
Net income (loss)	51,781	16,924
Capital expenditures	118,734	133,792
Water [Member] | Regulated [Member]
Segment Reporting Information [Line Items]
Operating revenues	216,197	200,220
Operations and maintenance expense	73,694	74,338
Depreciation and amortization	41,511	39,261
Operating income (loss)	86,506	72,865
Interest expense, net	25,495	23,658
Allowance for funds used during construction	2,912	4,056
Provision for income taxes	3,127	936
Net income (loss)	59,934	52,169
Capital expenditures	110,606	133,792
Natural Gas [Member] | Regulated [Member]
Segment Reporting Information [Line Items]
Operating revenues	38,544
Operations and maintenance expense	8,823
Purchased gas	12,770
Depreciation and amortization	4,569
Operating income (loss)	11,715
Interest expense, net	1,887
Allowance for funds used during construction	36
Provision for income taxes	(3,448)
Net income (loss)	13,398
Capital expenditures	8,128
Other [Member]
Segment Reporting Information [Line Items]
Operating revenues	844	912
Operations and maintenance expense	24,120	4,976
Purchased gas
Depreciation and amortization	165	149
Operating income (loss)	(24,724)	(5,426)
Interest expense, net	2,705	4,192
Allowance for funds used during construction
Change in fair value of interest rate swap agreements		34,782
Equity earnings in joint venture	(127)	543
Provision for income taxes	(6,803)	(9,106)
Net income (loss)	(21,551)	(35,245)
Capital expenditures