Commitments And Contingencies (Third-Party Power Purchases) (Details) $ in Millions	Sep. 30, 2016 USD ($)	Dec. 31, 2015 USD ($)
Long-term Purchase Commitment [Line Items]
Long-term agreements range, years	20
Total	$ 406	$ 50,000

Amount of the recorded obligation to transfer funds in the future for fixed or minimum amounts or quantities of goods or services at fixed or minimum prices (for example, as in take-or-pay contracts or throughput contracts).

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 440
-SubTopic 10
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=6394976&loc=d3e25383-109308

Name:	us-gaap_RecordedUnconditionalPurchaseObligation
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant