Regulatory Matters (Details 4) (USD $)	Mar. 31, 2014	Dec. 31, 2013
Detail of regulatory liabilities
Regulatory liabilities, current	$ 136,000,000	$ 99,000,000
Regulatory liabilities, non-current	783,702,000	801,297,000
Removal costs
Detail of regulatory liabilities
Regulatory liabilities, current	28,000,000	28,000,000
Regulatory liabilities, non-current	298,000,000	303,000,000
Asset retirement obligations
Detail of regulatory liabilities
Regulatory liabilities, non-current	253,000,000	266,000,000
Renewable energy standard
Detail of regulatory liabilities
Regulatory liabilities, current	35,000,000	33,000,000
Regulatory liabilities, non-current	16,000,000	15,000,000
Income taxes - change in rates
Detail of regulatory liabilities
Regulatory liabilities, current	1,000,000
Regulatory liabilities, non-current	73,000,000	74,000,000
Spent nuclear fuel
Detail of regulatory liabilities
Regulatory liabilities, current	5,000,000	6,000,000
Regulatory liabilities, non-current	37,000,000	36,000,000
Deferred gains on utility property
Detail of regulatory liabilities
Regulatory liabilities, current	2,000,000	2,000,000
Regulatory liabilities, non-current	9,000,000	10,000,000
Income taxes-deferred investment tax credit
Detail of regulatory liabilities
Regulatory liabilities, current	3,000,000	3,000,000
Regulatory liabilities, non-current	79,000,000	79,000,000
Demand side management
Detail of regulatory liabilities
Regulatory liabilities, current	34,000,000	27,000,000
Deferred Fuel and Purchased Power Costs
Detail of regulatory liabilities
Regulatory liabilities, current	19,000,000
Deferred fuel and purchased power - mark-to-market
Detail of regulatory liabilities
Regulatory liabilities, current	9,000,000
Other
Detail of regulatory liabilities
Regulatory liabilities, non-current	$ 19,000,000	$ 18,000,000