Organization, Summary of Significant Accounting Policies and Recent Developments (Tables)

12 Months Ended

Dec. 31, 2012

Accounting Policies [Abstract]

Range of depreciation rates

Source of Supply	1.15% - 3.44%	Transmission and Distribution (T&D):
Pumping	2.87% - 5.39%	T&D – Mains	1.10% - 3.13%
Water Treatment	1.65% - 7.09%	T&D – Services	2.12% - 3.16%
General Plant	2.08% - 17.84%	T&D – Other	1.61% - 4.63%

Allowance for Funds Used During Construction Rates

	2012	2011	2010
Middlesex	7.34%	7.54%	7.54%
Tidewater	7.91%	8.24%	8.24%