CONSOLIDATED STATEMENTS OF CHANGES IN COMMON SHAREHOLDERS' EQUITY (USD $) In Thousands, except Share data, unless otherwise specified	Total	GSWC	Common Stock [Member]	Common Stock [Member] GSWC	Earnings Reinvested in the Business	Earnings Reinvested in the Business GSWC
Balances at Dec. 31, 2011	$ 408,666us-gaap_StockholdersEquity	$ 384,806	$ 233,306	$ 228,936	$ 175,360	$ 155,870
Balances (in shares) at Dec. 31, 2011			37,578,000	146
Add:
Net Income	54,148us-gaap_NetIncomeLoss	39,220			54,148	39,220
Issuance of Common Shares	13,295		13,295
Issuance of Common Shares (in shares)	77,038		896,000
Exercise of stock options (in shares)	819,400
Tax benefit from employee stock-based awards	890	895	890	895
Compensation on stock-based awards	1,710	1,536	1,710	1,536
Dividend equivalent rights on stock-based awards not paid in cash	121	113	121	113
Deduct:
Dividends on Common Shares	24,130us-gaap_DividendsCommonStock	10,200			24,130	10,200
Dividend equivalent rights on stock-based awards	121	113			121	113
Balances at Dec. 31, 2012	454,579us-gaap_StockholdersEquity	416,257	249,322	231,480	205,257	184,777
Balances (in shares) at Dec. 31, 2012			38,474,000	146
Add:
Net Income	62,686us-gaap_NetIncomeLoss	48,642			62,686	48,642
Issuance of Common Shares		943		943
Issuance of Common Shares (in shares)	114,821
Exercise of stock options (in shares)	131,448
Exercise of stock options and other issuance of Common Shares	2,111		2,111
Exercise of stock options and other issuance of Common Shares (in shares)			247,000
Tax benefit from employee stock-based awards	1,026		1,026
Compensation on stock-based awards	1,362	1,171	1,362	1,171
Dividend equivalent rights on stock-based awards not paid in cash	140	127	140	127
Deduct:
Dividends on Common Shares	29,360us-gaap_DividendsCommonStock	29,400			29,360	29,400
Dividend equivalent rights on stock-based awards	140	127			140	127
Balances at Dec. 31, 2013	492,404us-gaap_StockholdersEquity	437,613	253,961	233,721	238,443	203,892
Balances (in shares) at Dec. 31, 2013			38,721,000	146
Add:
Net Income	61,058us-gaap_NetIncomeLoss	47,857			61,058	47,857
Issuance of Common Shares (in shares)	74,145
Exercise of stock options (in shares)	37,006
Exercise of stock options and other issuance of Common Shares	589		589
Exercise of stock options and other issuance of Common Shares (in shares)			111,000
Tax benefit from employee stock-based awards	533	514	533	514
Compensation on stock-based awards	1,508	1,206	1,508	1,206
Dividend equivalent rights on stock-based awards not paid in cash	197	166	197	166
Stock Repurchased During Period, Shares			545,000
Stock Repurchased During Period, Value	17,180		3,589		13,591
Deduct:
Dividends on Common Shares	32,111us-gaap_DividendsCommonStock	52,000			32,111	52,000
Dividend equivalent rights on stock-based awards	197	166			197	166
Balances at Dec. 31, 2014	$ 506,801us-gaap_StockholdersEquity	$ 435,190	$ 253,199	$ 235,607	$ 253,602	$ 199,583
Balances (in shares) at Dec. 31, 2014			38,287,000	146

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