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REGULATORY PROCEEDINGS (Details) - USD ($) | 3 Months Ended | 6 Months Ended | 12 Months Ended
--- | --- | --- | ---
Jun. 30, 2018 | Jun. 30, 2017 | Jun. 30, 2018 | Jun. 30, 2017 | Dec. 31, 2016
Other Proceedings [Abstract] |  |  |  |  |
Cumulative DSIC Rate | 3.63% |  | 3.63% |  | 4.71%
Eligible Plant Improvements - Cumulative Dollars |  |  | $ 24,700,000 |  | $ 16,600,000
Delaware [Member] |  |  |  |  |
Rate Proceedings [Abstract] |  |  |  |  |
Percentage of gross water sales |  |  | 15.00% |  |
Period to complete rate case by law |  |  | 7 months |  |
Delaware [Member] | Maximum [Member] |  |  |  |  |
Rate Proceedings [Abstract] |  |  |  |  |
Temporary annual rate increase subject to 15% gross water sales limitation |  |  | $ 2,500,000 |  |
Percentage of rate relief allowed should a rate case not complete |  |  | 15.00% |  |
Other Proceedings [Abstract] |  |  |  |  |
Distribution System Improvement Charge rate increase applied between base rate filings |  |  | 7.50% |  |
Distribution System Improvement Charge rate increase within a 12-month period |  |  | 5.00% |  |
Artesian Water [Member] |  |  |  |  |
Other Proceedings [Abstract] |  |  |  |  |
Revenue held in reserve pending outcome of TCJA impact to customers | $ 800,000 |  | $ 1,548,000 |  |
Revenue earned in DSIC rate increases | $ 0 | $ 787,000 | $ 0 | $ 1,543,000 |

X
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