Organization, Summary of Significant Accounting Policies and Recent Developments (Details)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Source of Supply | Minimum
Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service	1.15%	1.15%	1.15%
Source of Supply | Maximum
Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service	3.44%	3.44%	3.44%
Pumping | Minimum
Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service	2.87%	2.87%	2.87%
Pumping | Maximum
Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service	5.39%	5.39%	5.39%
Water Treatment | Minimum
Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service	1.65%	1.65%	1.65%
Water Treatment | Maximum
Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service	7.09%	7.09%	7.09%
General Plant | Minimum
Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service	2.08%	2.08%	2.08%
General Plant | Maximum
Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service	17.84%	17.84%	17.84%
T&D - Mains | Minimum
Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service	1.10%	1.10%	1.10%
T&D - Mains | Maximum
Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service	3.13%	3.13%	3.13%
T&D - Services | Minimum
Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service	2.12%	2.12%	2.12%
T&D - Services | Maximum
Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service	3.16%	3.16%	3.16%
T&D - Other | Minimum
Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service	1.61%	1.61%	1.61%
T&D - Other | Maximum
Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service	4.63%	4.63%	4.63%