Summary of Derivative Fair Value Balance (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Derivative [Line Items]
Regulatory and other long-term assets	$ 4,776	$ 7,909
Fair value adjustment to interest rate hedge	4,724	7,715
Interest Rate Swap
Derivative [Line Items]
Fair value adjustment to interest rate hedge	4,724	7,715
Other
Derivative [Line Items]
Regulatory and other long-term assets	$ 4,776	$ 7,909