Employee Benefit Plans Employee Benefit Plans 5 (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Pension Benefits
Employee benefit plans
Regulatory adjustment - over collection	$ (465)	$ (859)	$ (523)
GSWC | Pension Benefits
Employee benefit plans
Regulatory adjustment - over collection	(583)	$ (859)	$ (523)
Pension Costs and Other Postretirement Benefit Costs | GSWC
Employee benefit plans
Regulatory asset authorized under settlement	34,700
Two-way pension balancing account | Pension Costs and Other Postretirement Benefit Costs | GSWC
Employee benefit plans
Regulatory asset authorized under settlement	$ 1,700