Aquisitions Fair Value of Assets Acquired (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2012	Dec. 31, 2011	Dec. 10, 2012 Biddeford and Saco Water Company Acquisition [Member]
Business Acquisition [Line Items]
Public Utilities, Property, Plant and Equipment, Net	$ 455,439	$ 447,911			$ 19,411
Cash and Cash Equivalents	7,548	13,150	3,397	1,012	14
Accounts Receivable, Net, Current	12,136	11,526			628
Prepayments and Other Current Assets	3,357	2,824			545
Goodwill	31,685	31,685			7,708
Deferred Charges and Other Costs	8,251	8,180			554
Total Assets	586,096	578,975			28,860
Long-term Debt	178,731	178,475			9,263
Accounts Payable and Accrued Expenses	7,326	10,016			254
Other Current Liabilities	2,065	2,008			1,076
Advances for Construction	31,566	31,030			714
Contributions in Aid of Construction	77,349	77,372			2,568
Deferred Federal and State Income Taxes	43,947	40,869			1,668
Other Long-Term Liabilities	1,036	2,319			1,305
Liabilities					16,848
Assets, Net					$ 12,012