Borrowings and Other Financing Instruments, Intercompany Borrowing Arrangement and Other Short-Term Borrowings (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Short-term Debt [Line Items]
Notes payable to affiliates	$ 470	$ 470
Intercompany Borrowing Arrangement
Short-term Debt [Line Items]
Notes payable to affiliates	$ 500	$ 500
Weighted average interest rate at period end (in hundredths)	0.38%	0.24%