Utility Plant, Palo Verde and Other Jointly-Owned Utility Plant (Amortization of Intangible Plant Assets - Software) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Property, Plant and Equipment and Finite-Lived Intangible Assets [Line Items]
Number of years amortization expense prior reporting year	3 years
Number of years amortization expense after reporting year	5 years
Intangible
Property, Plant and Equipment and Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Amortization Expense	$ 7,683	$ 7,183	$ 6,668
Future Amortization Expense, 2014 (estimated)	7,372
Future Amortization Expense, 2015 (estimated)	6,540
Future Amortization Expense, 2016 (estimated)	5,980
Future Amortization Expense, 2017 (estimated)	5,326
Future Amortization Expense, 2018 (estimated)	$ 3,713
Minimum | Intangible
Property, Plant and Equipment and Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Useful Life	5 years
Maximum | Intangible
Property, Plant and Equipment and Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Useful Life	10 years