Utility Plant and Intangible Assets - By Major Asset Class (Details) - USD ($) $ in Thousands		Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Utility plant utilized in continuing operations by major asset class
Total utility plant, at cost		$ 2,279,621	$ 2,178,349
Less — accumulated depreciation		(624,472)	(606,231)
Construction work in progress		237,131	181,648
Net utility plant		1,892,280	1,753,766	$ 1,626,004
Water
Utility plant utilized in continuing operations by major asset class
Total utility plant, at cost		2,123,150	2,044,534
Water | Land
Utility plant utilized in continuing operations by major asset class
Total utility plant, at cost		18,290	18,427
Water | Intangible assets
Utility plant utilized in continuing operations by major asset class
Total utility plant, at cost		30,917	30,511
Water | Source of water supply
Utility plant utilized in continuing operations by major asset class
Total utility plant, at cost		111,112	109,918
Water | Pumping
Utility plant utilized in continuing operations by major asset class
Total utility plant, at cost		234,264	227,668
Water | Water treatment
Utility plant utilized in continuing operations by major asset class
Total utility plant, at cost		98,533	90,411
Water | Transmission and distribution
Utility plant utilized in continuing operations by major asset class
Total utility plant, at cost		1,489,974	1,431,437
Water | Other
Utility plant utilized in continuing operations by major asset class
Total utility plant, at cost		140,060	136,162
Electric:
Utility plant utilized in continuing operations by major asset class
Total utility plant, at cost		156,471	133,815
Electric: | Intangible assets
Utility plant utilized in continuing operations by major asset class
Total utility plant, at cost		1,200	1,200
Electric: | Transmission and distribution
Utility plant utilized in continuing operations by major asset class
Total utility plant, at cost		126,143	105,499
Electric: | Generation
Utility plant utilized in continuing operations by major asset class
Total utility plant, at cost		12,583	12,583
Electric: | Other
Utility plant utilized in continuing operations by major asset class
Total utility plant, at cost	[1]	17,745	15,733
GSWC
Utility plant utilized in continuing operations by major asset class
Less — accumulated depreciation		(543,135)	(530,925)
Construction work in progress		195,742	141,175
Net utility plant		1,735,534	1,616,718
GSWC | Water
Utility plant utilized in continuing operations by major asset class
Total utility plant, at cost		2,082,927	2,006,468
Net utility plant		1,735,534	1,616,718	$ 1,499,745
GSWC | Water | Land
Utility plant utilized in continuing operations by major asset class
Total utility plant, at cost		18,290	18,427
GSWC | Water | Intangible assets
Utility plant utilized in continuing operations by major asset class
Total utility plant, at cost		30,917	30,511
GSWC | Water | Source of water supply
Utility plant utilized in continuing operations by major asset class
Total utility plant, at cost		111,112	109,918
GSWC | Water | Pumping
Utility plant utilized in continuing operations by major asset class
Total utility plant, at cost		234,264	227,668
GSWC | Water | Water treatment
Utility plant utilized in continuing operations by major asset class
Total utility plant, at cost		98,533	90,411
GSWC | Water | Transmission and distribution
Utility plant utilized in continuing operations by major asset class
Total utility plant, at cost		1,489,974	1,431,437
GSWC | Water | Other
Utility plant utilized in continuing operations by major asset class
Total utility plant, at cost		99,837	98,096
GSWC | Electric:
Utility plant utilized in continuing operations by major asset class
Total utility plant, at cost		0	0
GSWC | Electric: | Transmission and distribution
Utility plant utilized in continuing operations by major asset class
Total utility plant, at cost		0	0
GSWC | Electric: | Generation
Utility plant utilized in continuing operations by major asset class
Total utility plant, at cost		0	0
GSWC | Electric: | Other
Utility plant utilized in continuing operations by major asset class
Total utility plant, at cost	[1]	$ 0	$ 0

[1]      Includes intangible assets of $1.2 million for the years ended December 31, 2023 and 2022 for studies performed.