CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2025	Dec. 31, 2024
Property, Plant and Equipment
Regulated utility plant, at cost	$ 2,849,671	$ 2,703,127
Non-utility property, at cost	49,505	44,697
Total	2,899,176	2,747,824
Less - accumulated depreciation	(658,307)	(648,199)
Net property, plant and equipment	2,240,869	2,099,625
Property, Plant and Equipment, Other, Net [Abstract]
Other property and investments	55,737	50,418
Current Assets
Cash and cash equivalents	26,073	26,661
Accounts receivable - customers, less allowance for doubtful accounts	46,577	37,699
Unbilled receivable	28,056	28,446
Receivable from the U.S. government (Note 2)	37,072	41,000
Other accounts receivable, less allowance for doubtful accounts	12,327	6,415
Income taxes receivable	0	65
Materials and supplies	16,955	15,140
Regulatory assets — current	49,358	50,504
Prepayments and other current assets	8,196	7,286
Contract assets (Note 2)	26,167	20,130
Total current assets	250,781	233,346
Other Assets
Unbilled revenue — receivable from the U.S. government (Note 2)	1,718	3,423
Receivable from the U.S. government (Note 2)	29,413	35,486
Contract assets (Note 2)	1,405	1,518
Operating lease right-of-use assets	6,638	8,028
Regulatory assets	27,117	27,101
Other	41,595	41,264
Total other assets	107,886	116,820
Total Assets	2,655,273	2,500,209
Capitalization
Common shares, no par value	398,010	355,143
Retained earnings	611,299	564,908
Total common shareholders’ equity	1,009,309	920,051
Long-term debt	790,261	640,382
Total capitalization	1,799,570	1,560,433
Current Liabilities
Notes payable to banks	5,000	124,000
Long-term debt — current	479	385
Accounts payable	81,664	88,591
Income taxes payable	27,343	481
Accrued other taxes	16,119	16,694
Accrued employee expenses	16,321	15,523
Accrued interest	11,450	8,133
Contract liabilities (Note 2)	10,420	5,662
Operating lease liabilities	2,081	2,074
Purchase power contract derivative at fair value (Note 5)	14,275	8,823
Other	12,323	15,159
Total current liabilities	197,475	285,525
Other Credits
Notes payable to banks	119,000	165,000
Advances for construction	75,770	69,856
Contributions in aid of construction – net	170,750	160,306
Deferred income taxes	190,986	180,173
Regulatory liabilities	47,291	22,926
Unamortized investment tax credits	890	942
Accrued pension and other postretirement benefits	32,043	33,816
Operating lease liabilities	4,959	6,394
Other	16,539	14,838
Total other credits	658,228	654,251
Commitments and Contingencies (Note 9)
Total Capitalization and Liabilities	2,655,273	2,500,209
GSWC
Property, Plant and Equipment
Total	2,605,544	2,472,625
Less - accumulated depreciation	(570,442)	(561,256)
Net property, plant and equipment	2,035,102	1,911,369
Property, Plant and Equipment, Other, Net [Abstract]
Other property and investments	53,081	47,753
Current Assets
Cash and cash equivalents	7,947	11,338
Accounts receivable - customers, less allowance for doubtful accounts	42,538	34,712
Unbilled receivable	22,816	19,417
Other accounts receivable, less allowance for doubtful accounts	10,703	3,122
Income taxes receivable	0	3,253
Materials and supplies	8,334	7,543
Regulatory assets — current	33,417	41,099
Prepayments and other current assets	6,393	5,880
Total current assets	132,148	126,484
Other Assets
Operating lease right-of-use assets	6,376	7,981
Other	38,840	38,394
Total other assets	45,216	46,375
Total Assets	2,265,547	2,131,981
Capitalization
Common shares, no par value	466,239	413,797
Retained earnings	435,687	392,036
Total common shareholders’ equity	901,926	805,833
Long-term debt	705,639	605,547
Total capitalization	1,607,565	1,411,380
Current Liabilities
Notes payable to banks	0	124,000
Long-term debt — current	479	385
Accounts payable	65,389	70,896
Income taxes payable	21,107	0
Accrued other taxes	13,281	14,285
Accrued employee expenses	12,842	12,271
Accrued interest	10,035	7,438
Operating lease liabilities	1,986	2,036
Other	11,575	14,468
Total current liabilities	137,087	245,779
Other Credits
Advances for construction	75,750	69,836
Contributions in aid of construction – net	170,750	160,306
Deferred income taxes	174,954	166,410
Regulatory liabilities	47,291	22,926
Unamortized investment tax credits	890	942
Accrued pension and other postretirement benefits	31,476	33,351
Operating lease liabilities	4,796	6,394
Other	14,988	14,657
Total other credits	520,895	474,822
Commitments and Contingencies (Note 9)
Total Capitalization and Liabilities	2,265,547	2,131,981
GSWC | Related Party
Current Assets
Receivable from affiliate	0	120
Current Liabilities
Intercompany payable to affiliate	$ 393	$ 0