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

12 Months Ended

Dec. 31, 2016

Organization Summary Of Significant Accounting Policies And Recent Developments [Abstract]

Range of depreciation rates

Source of Supply	1.15% -   3.44%	Transmission and Distribution (T&D):
Pumping	2.00% -   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%
Wastewater Collection	1.42% -   1.81%

Allowance for Funds Used During Construction Rates

	2016		2015		2014
Middlesex		6.73%		6.72%		7.03%
Tidewater		7.92%		7.92%		7.91%