CONSOLIDATED STATEMENTS OF CHANGES IN COMMON SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Total	GSWC	Common Stock [Member]	Common Stock [Member] GSWC	Earnings Reinvested in the Business	Earnings Reinvested in the Business GSWC
Common stock, shares outstanding			36,571,000	146
Balances at Dec. 31, 2016	$ 494,297	$ 446,770	$ 247,232	$ 240,482	$ 247,065	$ 206,288
Add:
Net Income	$ 69,367	53,757			69,367	53,757
Stock Issued During Period, Shares, New Issues	56,498		110,000
Exercise of stock options and other issuance of Common Shares	$ 909		$ 909
Stock-based compensation, net of taxes paid from shares withheld from employees related to net share settlements	1,789	1,527	1,789	1,527
Dividend equivalent rights on stock-based awards not paid in cash	194	172	194	172
Deduct:
Dividends on Common Shares	36,417	27,680			36,417	27,680
Dividend equivalent rights on stock-based awards	194	172			194	172
Balances at Dec. 31, 2017	529,945	474,374	$ 250,124	$ 242,181	279,821	232,193
Common stock, shares outstanding			36,681,000	146
Add:
Net Income	$ 63,871	48,012			63,871	48,012
Stock Issued During Period, Shares, New Issues	44,906		77,000	19
Exercise of stock options and other issuance of Common Shares	$ 546		$ 546
Stock Issued During Period, Value, New Issues		47,500
Stock-based compensation, net of taxes paid from shares withheld from employees related to net share settlements	2,798	2,539	2,798	$ 2,539
Dividend equivalent rights on stock-based awards not paid in cash	221	192	221	192
Deduct:
Dividends on Common Shares	38,937	68,850			38,937	68,850
Dividend equivalent rights on stock-based awards	221	192			221	192
Balances at Dec. 31, 2018	$ 558,223	$ 503,575	$ 253,689	$ 292,412	304,534	211,163
Common stock, shares outstanding	36,680,794	165	36,758,000	165
Add:
Net Income	$ 84,342	$ 66,663				66,663
Stock Issued During Period, Shares, New Issues	88,772		89,000
Exercise of stock options and other issuance of Common Shares	$ 519		$ 519
Stock-based compensation, net of taxes paid from shares withheld from employees related to net share settlements	1,148	1,150	1,148	$ 1,150
Dividend equivalent rights on stock-based awards not paid in cash	210	192	210	192
Deduct:
Dividends on Common Shares	42,702	20,200			42,702	20,200
Dividend equivalent rights on stock-based awards	210	192			210	192
Balances at Dec. 31, 2019	$ 601,530	$ 551,188	$ 255,566	$ 293,754	$ 345,964	$ 257,434
Common stock, shares outstanding	36,846,614	165	36,847,000	165