Commitments And Contingencies (MPG Site Estimated Future Costs And Recorded Liabilities) (Details) - Natural Gas Processing Plant [Member] $ in Millions	9 Months Ended
Sep. 30, 2019 USD ($)
Commitments and Contingencies [Line Items]
Current and non-current environmental liabilities	$ 19
IPL [Member]
Commitments and Contingencies [Line Items]
Current and non-current environmental liabilities	16
Minimum [Member]
Commitments and Contingencies [Line Items]
Range of estimated future costs	14
Minimum [Member] \| IPL [Member]
Commitments and Contingencies [Line Items]
Range of estimated future costs	12
Maximum [Member]
Commitments and Contingencies [Line Items]
Range of estimated future costs	31
Maximum [Member] \| IPL [Member]
Commitments and Contingencies [Line Items]
Range of estimated future costs	$ 25

Total costs accrued as of the balance sheet date for environmental loss contingencies.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=118942415&loc=d3e14326-108349

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 25
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6395460&loc=d3e13647-108346

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 30
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13207-110859

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