Acquisition (Details) people in Thousands, $ in Thousands	Jun. 01, 2020 USD ($) customerConnection waterSystem people	Jun. 30, 2020 USD ($)	Dec. 31, 2019 USD ($)
Business Acquisition [Line Items]
Goodwill		$ 31,132	$ 2,615
Rainier View Water Company
Business Acquisition [Line Items]
Number of people served | people	35
Number of customer connections | customerConnection	18,500
Water Systems | waterSystem	27
Rainier View Water Company
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross	$ 37,700
Assets acquired and liabilities assumed	32,600
Assets acquired and liabilities assumed, property, plant, and equipment	31,100
Recognized identifiable assets acquired and liabilities assumed, liabilities		$ 23,500
Recognized identifiable assets acquired and liabilities assumed, aid for construction	21,200
Goodwill	$ 28,500