Aquisitions Fair Value of Assets Acquired (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Business Acquisition [Line Items]
Public Utilities, Property, Plant and Equipment, Net	$ 447,911	$ 360,027
Cash and Cash Equivalents	13,150	1,012	952	5,437
Accounts Receivable, Net, Current	11,526	8,436
Prepayments and Other Current Assets	2,824	1,830
Goodwill	31,685	3,608
Deferred Charges and Other Costs	8,180	6,442
Total Assets	578,975	442,931
Long-term Debt	178,475	135,256
Accounts Payable and Accrued Expenses	10,016	7,166
Other Current Liabilities	2,008	586
Advances for Construction	31,030	32,517
Contributions in Aid of Construction	77,372	60,679
Deferred Federal and State Income Taxes	40,869	31,075
Other Long-Term Liabilities	2,319	115
Maine Water Company Acquisition [Member]
Business Acquisition [Line Items]
Public Utilities, Property, Plant and Equipment, Net		50,877
Cash and Cash Equivalents		1,607
Accounts Receivable, Net, Current		974
Prepayments and Other Current Assets		1,819
Goodwill		20,369
Deferred Charges and Other Costs		4,498
Total Assets		80,144
Long-term Debt		18,259
Accounts Payable and Accrued Expenses		1,137
Other Current Liabilities		1,453
Advances for Construction		1,186
Contributions in Aid of Construction		8,886
Deferred Federal and State Income Taxes		8,046
Other Long-Term Liabilities		4,152
Liabilities		43,119
Assets, Net		37,025
Biddeford and Saco [Member]
Business Acquisition [Line Items]
Public Utilities, Property, Plant and Equipment, Net		19,411
Cash and Cash Equivalents		14
Accounts Receivable, Net, Current		628
Prepayments and Other Current Assets		545
Goodwill		7,708
Deferred Charges and Other Costs		554
Total Assets		28,860
Long-term Debt		9,263
Accounts Payable and Accrued Expenses		254
Other Current Liabilities		1,076
Advances for Construction		714
Contributions in Aid of Construction		2,568
Deferred Federal and State Income Taxes		1,668
Other Long-Term Liabilities		1,305
Liabilities		16,848
Assets, Net		$ 12,012