CONSOLIDATED STATEMENTS OF CAPITALIZATION (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
Common stock, Par value (in dollars per share)	$ 0	$ 0
Common stock, shares authorized	60,000,000	60,000,000
Common stock, shares outstanding	39,082,470	38,151,027
Common Stock Shares Issued Not Disclosed	true
GSWC
Common stock, Par value (in dollars per share)	$ 0	$ 0
Common stock, shares authorized	1,000	1,000
Common stock, shares outstanding	178.3836	173.7586
6.81% notes due 2028
Interest rate per annum (as a percent)	6.81%	6.81%
6.81% notes due 2028 | GSWC
Interest rate per annum (as a percent)	6.81%	6.81%
6.59% notes due 2029
Interest rate per annum (as a percent)	6.59%	6.59%
6.59% notes due 2029 | GSWC
Interest rate per annum (as a percent)	6.59%	6.59%
7.875% notes due 2030
Interest rate per annum (as a percent)	7.875%	7.875%
7.875% notes due 2030 | GSWC
Interest rate per annum (as a percent)	7.875%	7.875%
7.23% notes due 2031
Interest rate per annum (as a percent)	7.23%	7.23%
7.23% notes due 2031 | GSWC
Interest rate per annum (as a percent)	7.23%	7.23%
6.00% notes due 2041
Interest rate per annum (as a percent)	6.00%	6.00%
6.00% notes due 2041 | GSWC
Interest rate per annum (as a percent)	6.00%	6.00%
3.45% notes due 2029
Interest rate per annum (as a percent)	3.45%	3.45%
3.45% notes due 2029 | GSWC
Interest rate per annum (as a percent)	3.45%	3.45%
5.87% notes due 2028
Interest rate per annum (as a percent)	5.87%	5.87%
5.87% notes due 2028 | GSWC
Interest rate per annum (as a percent)	5.87%	5.87%
2.17% notes due 2030
Interest rate per annum (as a percent)	2.17%	2.17%
2.17% notes due 2030 | GSWC
Interest rate per annum (as a percent)	2.17%	2.17%
2.90% notes due 2040
Interest rate per annum (as a percent)	2.90%	2.90%
2.90% notes due 2040 | GSWC
Interest rate per annum (as a percent)	2.90%	2.90%
4.548% note due 2032
Interest rate per annum (as a percent)	4.548%	4.548%
4.949% note due 2037
Interest rate per annum (as a percent)	4.949%	4.949%
5.12% notes due 2033
Interest rate per annum (as a percent)	5.12%	5.12%
5.12% notes due 2033 | GSWC
Interest rate per annum (as a percent)	5.12%	5.12%
5.22 % note due 2038
Interest rate per annum (as a percent)	5.22%	5.22%
5.22 % note due 2038 | GSWC
Interest rate per annum (as a percent)	5.22%	5.22%
5.50% notes due 2027
Interest rate per annum (as a percent)	5.50%
5.50% notes due 2027 | GSWC
Interest rate per annum (as a percent)	5.50%
6.12% notes due 2030
Interest rate per annum (as a percent)	6.12%
5.30% notes due 2032
Interest rate per annum (as a percent)	5.30%
5.30% notes due 2032 | GSWC
Interest rate per annum (as a percent)	5.30%
5.65% notes due 2037
Interest rate per annum (as a percent)	5.65%
5.65% notes due 2037 | GSWC
Interest rate per annum (as a percent)	5.65%
5.50% notes due 2026
Interest rate per annum (as a percent)	5.50%	5.50%
5.50% notes due 2026 | GSWC
Interest rate per annum (as a percent)	5.50%	5.50%