Derivatives (Volumes Of Outstanding Derivative Contracts, In Megawatt Hours Unless Otherwise Specified) (Detail)	3 Months Ended		12 Months Ended
	Jun. 30, 2014		Dec. 31, 2013
Derivative [Line Items]
Derivatives expiration, lower (year)	2019 years		2019 years
Derivatives expiration, higher (year)	2023 years		2022 years
Forwards And Swaps [Member] | Natural Gas [Member]
Derivative [Line Items]
Less Than 1 Year	253,455,503	[1],[2],[3]	243,213,288	[4]
Greater Than 1 Year but Less Than 3 Years	68,107,500	[1],[2],[3]	79,735,000	[4]
Greater Than 3 Years but Less Than 5 Years	5,370,000	[1],[2],[3]	8,892,500	[1],[2],[3]
Greater Than 5 Years	0	[1],[2],[3],[5]	0	[1],[2],[3],[6]
Forwards And Swaps [Member] | Electricity [Member]
Derivative [Line Items]
Less Than 1 Year	1,750,584	[1]	2,537,023	[1]
Greater Than 1 Year but Less Than 3 Years	1,956,498	[1]	2,009,505	[1]
Greater Than 3 Years but Less Than 5 Years	1,735,012	[1]	2,008,046	[1]
Greater Than 5 Years	1,200,183	[1],[5]	1,534,695	[1],[6]
Options [Member] | Natural Gas [Member]
Derivative [Line Items]
Less Than 1 Year	118,345,529	[1],[2],[3]	169,123,208	[1],[2],[3]
Greater Than 1 Year but Less Than 3 Years	56,101,311	[1],[2],[3]	87,689,708
Greater Than 3 Years but Less Than 5 Years	1,800,000	[1],[2],[3]	3,450,000
Greater Than 5 Years	0	[1],[2],[3],[5]	0	[1],[2],[3],[6]
Congestion Revenue Rights [Member] | Electricity [Member]
Derivative [Line Items]
Less Than 1 Year	60,291,148	[1]	73,510,440	[1]
Greater Than 1 Year but Less Than 3 Years	86,200,035	[1]	83,747,782	[1]
Greater Than 3 Years but Less Than 5 Years	50,662,422	[1]	63,718,517	[1]
Greater Than 5 Years	25,365,949	[1],[5]	29,945,852	[1],[6]

[1] Amounts shown reflect the total gross derivative volumes by commodity type that are expected to settle in each period.

[2] Amounts shown are for the combined positions of the electric fuels and core gas portfolios.

[3] Million British Thermal Units.

[4] The costs related to price risk management activities are recoverable through customer rates, therefore, balancing account revenue is recorded for amounts settled and purchased and there is no impact to net income. Unrealized gains and losses are deferred in regulatory liabilities and assets.

[5] Derivatives in this category expire between 2019 and 2023.

[6] Derivatives in this category expire between 2019 and 2022.