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Revenue from Contract with Customers - Additional Information (Details) - USD ($) $ in Billions | 3 Months Ended
--- | ---
Mar. 31, 2019 | Mar. 31, 2018
Disaggregation of Revenue [Line Items] |  |
Revenue, remaining performance obligation | $ 3.2 |
ASUS | Contracted Services |  |
Disaggregation of Revenue [Line Items] |  |
Period of fixed price contracts to operate and maintain water systems at various military bases | 50 years |
ASUS | Minimum |  |
Disaggregation of Revenue [Line Items] |  |
Revenue, remaining performance obligation, expected timing of satisfaction, explanation | P36Y |
ASUS | Maximum |  |
Disaggregation of Revenue [Line Items] |  |
Revenue, remaining performance obligation, expected timing of satisfaction, explanation | P49Y |
Sales | GOLDEN STATE WATER COMPANY | Water Service Utility Operations [Member] |  |
Disaggregation of Revenue [Line Items] |  |
Concentration Risk, Percentage | 90.00% | 90.00%
Sales | GOLDEN STATE WATER COMPANY | Electric Service Utility Operations |  |
Disaggregation of Revenue [Line Items] |  |
Concentration Risk, Percentage | 85.00% | 85.00%

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- Definition For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 275 -SubTopic 10 -Section 50 -Paragraph 18 -URI http://asc.fasb.org/extlink&oid=84177426&loc=d3e6351-108592 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 20 -URI http://asc.fasb.org/extlink&oid=77997519&loc=d3e13531-108611 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 275 -SubTopic 10 -Section 50 -Paragraph 20 -URI http://asc.fasb.org/extlink&oid=84177426&loc=d3e6404-108592 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 21 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=77997519&loc=d3e13537-108611 + Details
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