Summary of Significant Accounting Policies (Advances for Construction and Contributions in Aid of Construction) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012
Property, Plant and Equipment [Line Items]
Refund period for advances for construction received after 1981	40 years
Estimated Refunds of Advances for Construction [Abstract]
2013	$ 2,326
2014	2,325
2015	2,326
2016	2,325
2017	2,326
Thereafter	$ 56,649
Amortization period for taxes paid relating to advances and contributions	40 years