Derivatives (Gains And Losses On Derivative Instruments) (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2017		Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Net unrealized loss - regulatory assets and liabilities	$ (6)	[1]	$ (29)	$ (58)	$ 30
Realized loss - cost of electricity	(4)	[2]	(7)	(8)	(48)
Realized loss - cost of natural gas	(1)		(9)	(5)	(15)
Total commodity risk	$ (11)		$ (45)	$ (71)	$ (33)

[1] Unrealized gains and losses on commodity risk-related derivative instruments are recorded to regulatory liabilities or assets, respectively, rather than being recorded to the Condensed Consolidated Statements of Income. These amounts exclude the impact of cash collateral postings.

[2] These amounts are fully passed through to customers in rates. Accordingly, net income was not impacted by realized amounts on these instruments.