| Document and Entity Information | Sep. 04, 2019 |
| Cover [Abstract] | |
| Entity Registrant Name | CONNECTICUT WATER SERVICE INC / CT |
| Amendment Flag | false |
| Entity Central Index Key | 0000276209 |
| Document Type | 8-K |
| Document Period End Date | Sep. 4, 2019 |
| Entity Incorporation State Country Code | CT |
| Entity File Number | 0-8084 |
| Entity Tax Identification Number | 06-0739839 |
| Entity Address, Address Line One | 93 West Main Street |
| Entity Address, City or Town | Clinton |
| Entity Address, State or Province | CT |
| Entity Address, Postal Zip Code | 06413 |
| City Area Code | 860 |
| Local Phone Number | 669-8636 |
| Security 12b Title | Common Stock, without par value |
| Trading Symbol | CTWS |
| Security Exchange Name | NASDAQ |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
