Reportable Business Segments (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Segment Reporting Information [Line Items]
Revenues		$ 824	$ 1,183	$ 2,641	$ 3,714
Operating Income (Loss)		27	39	187	227
Assets		10,501		10,501		$ 11,045
Equity in earnings of unconsolidated affiliates, net		43	71	95	162
Investment in unconsolidated affiliates		4,471		4,471		4,521
Natural Gas Distribution
Segment Reporting Information [Line Items]
Revenues		420	526	1,605	2,004
Operating Income (Loss)		19	30	165	192
Energy Services
Segment Reporting Information [Line Items]
Revenues		404	657	1,036	1,709
Operating Income (Loss)		9	11	22	37
Midstream Investments (1)
Segment Reporting Information [Line Items]
Revenues	[1]	0	0	0	0
Operating Income (Loss)	[1]	0	0	0	0
Other Operations
Segment Reporting Information [Line Items]
Revenues		0	0	0	1
Operating Income (Loss)		(1)	(2)	0	(2)
Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenues		(11)	(25)	(37)	(66)
Assets		(823)		(823)		(964)
Intersegment Eliminations | Natural Gas Distribution
Segment Reporting Information [Line Items]
Revenues		(7)	(6)	(15)	(15)
Intersegment Eliminations | Energy Services
Segment Reporting Information [Line Items]
Revenues		(4)	(19)	(22)	(51)
Intersegment Eliminations | Midstream Investments (1)
Segment Reporting Information [Line Items]
Revenues	[1]	0	0	0	0
Intersegment Eliminations | Other Operations
Segment Reporting Information [Line Items]
Revenues		0	0	0	0
Operating Segments [Member] | Natural Gas Distribution
Segment Reporting Information [Line Items]
Assets		5,301		5,301		5,464
Operating Segments [Member] | Energy Services
Segment Reporting Information [Line Items]
Assets		837		837		978
Operating Segments [Member] | Midstream Investments (1)
Segment Reporting Information [Line Items]
Assets	[1]	4,471		4,471		4,521
Operating Segments [Member] | Other Operations
Segment Reporting Information [Line Items]
Assets		715		715		1,046
Southeast Supply Header LLC [Member]
Segment Reporting Information [Line Items]
Equity in earnings of unconsolidated affiliates, net	[2]	0	2	0	5
Investment in unconsolidated affiliates	[2]	0		0		1
Southeast Supply Header LLC [Member] | Midstream Investments (1)
Segment Reporting Information [Line Items]
Equity in earnings of unconsolidated affiliates, net		0	2	0	5
Investment in unconsolidated affiliates		0		0		1
Enable Midstream Partners [Member]
Segment Reporting Information [Line Items]
Equity in earnings of unconsolidated affiliates, net		43	69	95	157
Investment in unconsolidated affiliates		4,471		4,471		4,520
Enable Midstream Partners [Member] | Midstream Investments (1)
Segment Reporting Information [Line Items]
Equity in earnings of unconsolidated affiliates, net		43	$ 69	95	$ 157
Investment in unconsolidated affiliates		$ 4,471		$ 4,471		$ 4,520

[1] Midstream Investments’ equity earnings are as follows: Three Months Ended June 30, Six Months Ended June 30, 2015 2014 2015 2014 (in millions)Enable $43 $69 $95 $157SESH — 2 — 5 Total $43 $71 $95 $162Midstream Investments’ total assets are as follows: June 30, 2015 December 31, 2014 (in millions)Enable $4,471 $4,520SESH — 1 Total $4,471 $4,521

[2] CERC disposed of its remaining interest in SESH on June 30, 2015.