Schedule of Long-term Debt Instruments [Table Text Block] | Long-Term Debt at December 31, consisted of the following: | | | | | | | | | | | (in thousands) | 2016 | | 2015 | Connecticut Water Service, Inc.: | | | | 4.09% | | Term Loan Note and Supplement A, Due 2027 | $ | 13,437 |
| | $ | 14,472 |
| The Connecticut Water Company: | | | | Var. | | 2004 Series Variable Rate, Due 2029 | 12,500 |
| | 12,500 |
| Var. | | 2004 Series A, Due 2028 | 5,000 |
| | 5,000 |
| Var. | | 2004 Series B, Due 2028 | 4,550 |
| | 4,550 |
| 5.10% | | 2009 A Series, Due 2039 | — |
| | 19,930 |
| 5.00% | | 2011 A Series, Due 2021 | 23,115 |
| | 23,303 |
| 3.16% | | CoBank Note Payable, Due 2020 | 8,000 |
| | 8,000 |
| 3.51% | | CoBank Note Payable, Due 2022 | 14,795 |
| | 14,795 |
| 4.29% | | CoBank Note Payable, Due 2028 | 17,020 |
| | 17,020 |
| 4.72% | | CoBank Note Payable, Due 2032 | 14,795 |
| | 14,795 |
| 4.75% | | CoBank Note Payable, Due 2033 | 14,550 |
| | 14,550 |
| 4.36% | | CoBank Note Payable, Due May 2036 | 30,000 |
| | — |
| 4.04% | | CoBank Note Payable, Due July 2036 | 19,930 |
| | — |
| Total The Connecticut Water Company | 164,255 |
| | 134,443 |
| The Maine Water Company: | | | | 8.95% | | 1994 Series G, Due 2024 | 7,200 |
| | 8,100 |
| 2.68% | | 1999 Series J, Due 2019 | 254 |
| | 339 |
| 0.00% | | 2001 Series K, Due 2031 | 615 |
| | 656 |
| 2.58% | | 2002 Series L, Due 2022 | 67 |
| | 75 |
| 1.53% | | 2003 Series M, Due 2023 | 341 |
| | 361 |
| 1.73% | | 2004 Series N, Due 2024 | 371 |
| | 401 |
| 0.00% | | 2004 Series O, Due 2034 | 120 |
| | 127 |
| 1.76% | | 2006 Series P, Due 2026 | 391 |
| | 411 |
| 1.57% | | 2009 Series R, Due 2029 | 217 |
| | 227 |
| 0.00% | | 2009 Series S, Due 2029 | 583 |
| | 628 |
| 0.00% | | 2009 Series T, Due 2029 | 1,634 |
| | 1,760 |
| 0.00% | | 2012 Series U, Due 2042 | 154 |
| | 160 |
| 1.00% | | 2013 Series V, Due 2033 | 1,335 |
| | 1,360 |
| 2.52% | | CoBank Note Payable, Due 2017 | 1,965 |
| | 1,965 |
| 4.24% | | CoBank Note Payable, Due 2024 | 4,500 |
| | 4,500 |
| 7.72% | | Series L, Due 2018 | 2,250 |
| | 2,250 |
| 2.40% | | Series N, Due 2022 | 1,101 |
| | 1,176 |
| 1.86% | | Series O, Due 2025 | 790 |
| | 830 |
| 2.23% | | Series P, Due 2028 | 1,294 |
| | 1,324 |
| 0.01% | | Series Q, Due 2035 | 1,771 |
| | 1,864 |
| 1.00% | | Series R, Due 2025 | 2,250 |
| | 2,488 |
| Various | | Various Capital Leases | 8 |
| | 17 |
| Total The Maine Water Company | 29,211 |
| | 31,019 |
| Add: Acquisition Fair Value Adjustment | 321 |
| | 562 |
| Less: Current Portion | (4,859 | ) | | (2,842 | ) | Less: Unamortized Debt Issuance Expense | (5,318 | ) | | (5,786 | ) | Total Long-Term Debt | $ | 197,047 |
| | $ | 171,868 |
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