Long-Term Debt Long-Term Debt Parenthetical (Details)	Dec. 31, 2012	Dec. 31, 2011
Connecticut Water Service Term Loan Note and Supplement A [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.09%	4.09%
Subsidiaries [Member] | Unsecured Water Facilities Revenue Refinancing Bonds Series A Issued 1998, Due 2028 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.05%	5.05%
Subsidiaries [Member] | Unsecured Water Facilities Revenue Refinancing Bonds Series B Issued 1998, Due 2028 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.13%	5.13%
Subsidiaries [Member] | Unsecured Water Facilities Revenue Refinancing Bonds Series A Issued 2003, Due 2020 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.40%	4.40%
Subsidiaries [Member] | Unsecured Water Facilities Revenue Refinancing Bonds Series C Issued 2003, Due 2022 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.00%	5.00%
Subsidiaries [Member] | Unsecured Water Facilities Revenue Refinancing Bonds Series A 2005, Due 2040 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.00%	5.00%
Subsidiaries [Member] | Unsecured Water Facilities Revenue Refinancing Bonds Series A Issued 2007, Due 2037 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.00%	5.00%
Subsidiaries [Member] | Unsecured Water Facilities Revenue Refinancing Bonds Series A Issued 2009, Due 2039 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.10%	5.10%
Subsidiaries [Member] | Unsecured Water Facilities Revenue Refinancing Bonds Series A Issued 2011 Due 2021 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.00%	5.00%
Maine Water Company [Member] | Maine Water Company Series G [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	9.00%	9.00%
Maine Water Company [Member] | Maine Water Company Series J [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	3.00%	3.00%
Maine Water Company [Member] | Maine Water Company Series K [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	0.00%	0.00%
Maine Water Company [Member] | Maine Water Company Series L [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	3.00%	3.00%
Maine Water Company [Member] | Maine Water Company Series M [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	2.00%	2.00%
Maine Water Company [Member] | Maine Water Company Series N [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	2.00%	2.00%
Maine Water Company [Member] | Maine Water Company Series O [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	0.00%	0.00%
Maine Water Company [Member] | Maine Water Company Series P [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	2.00%	2.00%
Maine Water Company [Member] | Maine Water Company Series R [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	2.00%	2.00%
Maine Water Company [Member] | Maine Water Company Series S [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	0.00%	0.00%
Maine Water Company [Member] | Maine Water Company Series T [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	0.00%	0.00%