Utility Plant Components of Utility Plant (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Property, Plant and Equipment [Line Items]
Land	$ 12,512	$ 10,623
Source of Supply	33,627	29,687
Pumping Equipment	35,337	30,653
Water Treatment	75,684	56,799
Public Utilities, Property, Plant and Equipment, Transmission and Distribution	411,923	325,174
General Plant	47,444	39,619
Plant Held for Future Use Amount	437	472
Acquisition Adjustment	(5,177)	(5,487)
Utility Plant	$ 611,787	$ 487,540