Regulatory Matters (Details 4) (USD $)	Jun. 30, 2014	Dec. 31, 2013
Detail of regulatory liabilities
Regulatory liabilities, current	$ 114,000,000	$ 99,000,000
Regulatory liabilities, non-current	809,442,000	801,297,000
Removal costs
Detail of regulatory liabilities
Regulatory liabilities, current	29,000,000	28,000,000
Regulatory liabilities, non-current	293,000,000	303,000,000
Asset retirement obligations
Detail of regulatory liabilities
Regulatory liabilities, non-current	274,000,000	266,000,000
Renewable energy standard
Detail of regulatory liabilities
Regulatory liabilities, current	35,000,000	33,000,000
Regulatory liabilities, non-current	11,000,000	15,000,000
Income taxes - change in rates
Detail of regulatory liabilities
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	36,000,000	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	94,000,000	79,000,000
Demand side management
Detail of regulatory liabilities
Regulatory liabilities, current	35,000,000	27,000,000
Deferred fuel and purchased power - mark-to-market
Detail of regulatory liabilities
Regulatory liabilities, current	4,000,000
Other
Detail of regulatory liabilities
Regulatory liabilities, current	1,000,000
Regulatory liabilities, non-current	$ 19,000,000	$ 18,000,000