Derivative Instruments Summary of Derivative Activity (Details) $ in Millions		3 Months Ended		12 Months Ended
		Mar. 31, 2020 USD ($) Bcf	Mar. 31, 2019 USD ($)	Dec. 31, 2019 USD ($) Bcf
Derivatives, Fair Value [Line Items]
Derivative Assets Fair Value		$ 346		$ 292
Derivative Liabilities Fair Value		1,026		1,144
Derivative Asset		45		47
Cumulative Amount of Fair Value Hedging Adjustment Included in the Carrying Amount of Hedged Item		(20)		(13)
Total amounts presented in the statements of income in which the effects of hedges are recorded		64	$ 47
Gain (loss) on derivative instruments not designated as hedging instruments		210	(82)
Aggregate fair value of derivatives containing material adverse change provisions in a net liability position		1		1
Fair value of collateral already posted		0		0
Additional collateral required to be posted if credit risk contingent features triggered		1		1
Interest Rate Contract [Member] | Not Designated as Hedging Instrument [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Assets Fair Value		0		0
Derivative Liabilities Fair Value		$ 26		$ 10
Energy Related Derivative [Member]
Derivatives, Fair Value [Line Items]
Derivative gross volume notional amount (in Bcf) | Bcf		2,126		2,226
Gross Amounts Recognized	[1]	$ 104		$ 51
Gross Amounts Offset in the Consolidated Balance Sheets		50		63
Net amount presented in the consolidated balance sheets	[2]	154		114
Energy Related Derivative [Member] | Current Assets Held for Sale [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset	[2]	213		136
Gross Amounts Recognized	[1]	346		224
Gross Amounts Offset		(133)		(88)
Energy Related Derivative [Member] | Non-current assets held for sale [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset	[2]	0		58
Gross Amounts Recognized	[1]	0		68
Gross Amounts Offset		0		(10)
Energy Related Derivative [Member] | Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Gross Amounts Recognized		(9)		(7)	[1]
Gross Amounts Offset		0		0
Derivative Liability		(9)		(7)	[2]
Energy Related Derivative [Member] | Current liabilities held for sale [Member]
Derivatives, Fair Value [Line Items]
Gross Amounts Recognized		(219)		(180)	[1]
Gross Amounts Offset		183		136
Derivative Liability		(36)		(44)	[2]
Energy Related Derivative [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Gross Amounts Recognized		(14)		(15)	[1]
Gross Amounts Offset		0		0
Derivative Liability		(14)		(15)	[2]
Energy Related Derivative [Member] | Non-current liabilities held for sale [Member]
Derivatives, Fair Value [Line Items]
Gross Amounts Recognized		0		(39)	[1]
Gross Amounts Offset		0		25
Derivative Liability		0		(14)	[2]
Energy Related Derivative [Member] | Not Designated as Hedging Instrument [Member] | Current Assets Held for Sale [Member]
Derivatives, Fair Value [Line Items]
Derivative Assets Fair Value	[3],[4],[5]	215		139
Derivative Liabilities Fair Value	[3],[4],[5]	2		3
Energy Related Derivative [Member] | Not Designated as Hedging Instrument [Member] | Non-current assets held for sale [Member]
Derivatives, Fair Value [Line Items]
Derivative Assets Fair Value	[3],[4],[5]	0		58
Derivative Liabilities Fair Value	[3],[4],[5]	0		0
Energy Related Derivative [Member] | Not Designated as Hedging Instrument [Member] | Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Assets Fair Value		0		0	[3],[4],[5]
Derivative Liabilities Fair Value		9		7	[3],[4],[5]
Energy Related Derivative [Member] | Not Designated as Hedging Instrument [Member] | Current liabilities held for sale [Member]
Derivatives, Fair Value [Line Items]
Derivative Assets Fair Value		113		73	[3],[4],[5]
Derivative Liabilities Fair Value		217		177	[3],[4],[5]
Energy Related Derivative [Member] | Not Designated as Hedging Instrument [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Assets Fair Value		0		0	[3],[4],[5]
Derivative Liabilities Fair Value		14		15	[3],[4],[5]
Energy Related Derivative [Member] | Not Designated as Hedging Instrument [Member] | Non-current liabilities held for sale [Member]
Derivatives, Fair Value [Line Items]
Derivative Assets Fair Value		0		10	[3],[4],[5]
Derivative Liabilities Fair Value		$ 0		$ 39	[3],[4],[5]
Energy Related Derivative [Member] | Long [Member]
Derivatives, Fair Value [Line Items]
Derivative gross volume notional amount (in Bcf) | Bcf		232		374
IDS Derivative [Member] | Not Designated as Hedging Instrument [Member] | Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Assets Fair Value		$ 0		$ 0
Derivative Liabilities Fair Value		758		893
CERC Corp [Member]
Derivatives, Fair Value [Line Items]
Derivative Assets Fair Value		346		292
Derivative Liabilities Fair Value		219		219
Derivative Asset		45		47
Cumulative Amount of Fair Value Hedging Adjustment Included in the Carrying Amount of Hedged Item		(20)		(13)
Total amounts presented in the statements of income in which the effects of hedges are recorded		6	10
Gain (loss) on derivative instruments not designated as hedging instruments		75	4
Aggregate fair value of derivatives containing material adverse change provisions in a net liability position		1		1
Fair value of collateral already posted		0		0
Additional collateral required to be posted if credit risk contingent features triggered		$ 1		$ 1
CERC Corp [Member] | Energy Related Derivative [Member]
Derivatives, Fair Value [Line Items]
Derivative gross volume notional amount (in Bcf) | Bcf		2,126		2,226
Gross Amounts Recognized	[1]	$ 127		$ 73
Gross Amounts Offset in the Consolidated Balance Sheets		50		63
Net amount presented in the consolidated balance sheets	[2]	177		136
CERC Corp [Member] | Energy Related Derivative [Member] | Current Assets Held for Sale [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset		213		136	[2]
Gross Amounts Recognized		346		224	[1]
Gross Amounts Offset		(133)		(88)
CERC Corp [Member] | Energy Related Derivative [Member] | Non-current assets held for sale [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset		0		58	[2]
Gross Amounts Recognized		0		68	[1]
Gross Amounts Offset		0		(10)
CERC Corp [Member] | Energy Related Derivative [Member] | Current liabilities held for sale [Member]
Derivatives, Fair Value [Line Items]
Gross Amounts Recognized		(219)		(180)	[1]
Gross Amounts Offset		183		136
Derivative Liability		(36)		(44)	[2]
CERC Corp [Member] | Energy Related Derivative [Member] | Non-current liabilities held for sale [Member]
Derivatives, Fair Value [Line Items]
Gross Amounts Recognized		0		(39)	[1]
Gross Amounts Offset		0		25
Derivative Liability		0		(14)	[2]
CERC Corp [Member] | Energy Related Derivative [Member] | Not Designated as Hedging Instrument [Member] | Current Assets Held for Sale [Member]
Derivatives, Fair Value [Line Items]
Derivative Assets Fair Value		215		139	[6],[7],[8]
Derivative Liabilities Fair Value		2		3	[6],[7],[8]
CERC Corp [Member] | Energy Related Derivative [Member] | Not Designated as Hedging Instrument [Member] | Non-current assets held for sale [Member]
Derivatives, Fair Value [Line Items]
Derivative Assets Fair Value		0		58	[6],[7],[8]
Derivative Liabilities Fair Value		0		0	[6],[7],[8]
CERC Corp [Member] | Energy Related Derivative [Member] | Not Designated as Hedging Instrument [Member] | Current liabilities held for sale [Member]
Derivatives, Fair Value [Line Items]
Derivative Assets Fair Value		113		73	[6],[7],[8]
Derivative Liabilities Fair Value		217		177	[6],[7],[8]
CERC Corp [Member] | Energy Related Derivative [Member] | Not Designated as Hedging Instrument [Member] | Non-current liabilities held for sale [Member]
Derivatives, Fair Value [Line Items]
Derivative Assets Fair Value		0		10	[6],[7],[8]
Derivative Liabilities Fair Value		$ 0		$ 39	[6],[7],[8]
CERC Corp [Member] | Energy Related Derivative [Member] | Long [Member]
Derivatives, Fair Value [Line Items]
Derivative gross volume notional amount (in Bcf) | Bcf		232		374
Fair Value Hedging [Member] | Energy Related Derivative [Member] | Designated as Fair Value Hedge [Member] | Current liabilities held for sale [Member]
Derivatives, Fair Value [Line Items]
Derivative Assets Fair Value	[3],[4],[5]	$ 18		$ 12
Derivative Liabilities Fair Value	[3],[4],[5]	0		0
Fair Value Hedging [Member] | CERC Corp [Member] | Energy Related Derivative [Member] | Designated as Fair Value Hedge [Member] | Current liabilities held for sale [Member]
Derivatives, Fair Value [Line Items]
Derivative Assets Fair Value		18		12	[6],[7],[8]
Derivative Liabilities Fair Value		0		0	[6],[7],[8]
Non-utility Natural Gas Expense [Member] | Energy Related Derivative [Member]
Derivatives, Fair Value [Line Items]
Gain (loss) on derivative instruments not designated as hedging instruments		75	4
Non-utility Natural Gas Expense [Member] | CERC Corp [Member] | Energy Related Derivative [Member]
Derivatives, Fair Value [Line Items]
Gain (loss) on derivative instruments not designated as hedging instruments		75	4
Non-utility Natural Gas Expense [Member] | Fair Value Hedging [Member] | Energy Related Derivative [Member]
Derivatives, Fair Value [Line Items]
Change in unrealized gain (loss) on fair value hedging instruments	[9]	(7)	(6)
Amounts excluded from effectiveness testing recognized in earnings immediately	[9]	(38)	(14)
Non-utility Natural Gas Expense [Member] | Fair Value Hedging [Member] | Energy Related Derivative [Member] | Designated as Fair Value Hedge [Member]
Derivatives, Fair Value [Line Items]
Change in unrealized gain (loss) on fair value hedging instruments	[9]	7	6
Non-utility Natural Gas Expense [Member] | Fair Value Hedging [Member] | CERC Corp [Member] | Energy Related Derivative [Member]
Derivatives, Fair Value [Line Items]
Change in unrealized gain (loss) on fair value hedging instruments	[9]	(7)	(6)
Amounts excluded from effectiveness testing recognized in earnings immediately	[9]	(38)	(14)
Non-utility Natural Gas Expense [Member] | Fair Value Hedging [Member] | CERC Corp [Member] | Energy Related Derivative [Member] | Designated as Fair Value Hedge [Member]
Derivatives, Fair Value [Line Items]
Change in unrealized gain (loss) on fair value hedging instruments	[9]	7	6
Gains (Losses) in Other Income (Expense) [Member] | IDS Derivative [Member]
Derivatives, Fair Value [Line Items]
Gain (loss) on derivative instruments not designated as hedging instruments		135	(86)
Natural gas inventory [Member] | Energy Related Derivative [Member] | Current Assets Held for Sale [Member]
Derivatives, Fair Value [Line Items]
Cumulative Amount of Fair Value Hedging Adjustment Included in the Carrying Amount of Hedged Item		(19)		(13)
Natural gas inventory [Member] | CERC Corp [Member] | Energy Related Derivative [Member] | Current Assets Held for Sale [Member]
Derivatives, Fair Value [Line Items]
Cumulative Amount of Fair Value Hedging Adjustment Included in the Carrying Amount of Hedged Item		(19)		(13)
Natural gas inventory [Member] | Fair Value Hedging [Member] | Energy Related Derivative [Member] | Current Assets Held for Sale [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset		45		47
Natural gas inventory [Member] | Fair Value Hedging [Member] | CERC Corp [Member] | Energy Related Derivative [Member] | Current Assets Held for Sale [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset		45		$ 47
Borrowed gas [Member] | Energy Related Derivative [Member] | Current liabilities held for sale [Member]
Derivatives, Fair Value [Line Items]
Cumulative Amount of Fair Value Hedging Adjustment Included in the Carrying Amount of Hedged Item		0
Borrowed gas [Member] | CERC Corp [Member] | Energy Related Derivative [Member] | Current liabilities held for sale [Member]
Derivatives, Fair Value [Line Items]
Cumulative Amount of Fair Value Hedging Adjustment Included in the Carrying Amount of Hedged Item		0
Borrowed gas [Member] | Fair Value Hedging [Member] | Energy Related Derivative [Member] | Current liabilities held for sale [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability		(2)
Borrowed gas [Member] | Fair Value Hedging [Member] | CERC Corp [Member] | Energy Related Derivative [Member] | Current liabilities held for sale [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability		(2)
Gas Imbalance Receivable [Member] | Energy Related Derivative [Member] | Current Assets Held for Sale [Member]
Derivatives, Fair Value [Line Items]
Cumulative Amount of Fair Value Hedging Adjustment Included in the Carrying Amount of Hedged Item		(2)
Gas Imbalance Receivable [Member] | CERC Corp [Member] | Energy Related Derivative [Member] | Current Assets Held for Sale [Member]
Derivatives, Fair Value [Line Items]
Cumulative Amount of Fair Value Hedging Adjustment Included in the Carrying Amount of Hedged Item		(2)
Gas Imbalance Receivable [Member] | Fair Value Hedging [Member] | Energy Related Derivative [Member] | Current Assets Held for Sale [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset		2
Gas Imbalance Receivable [Member] | Fair Value Hedging [Member] | CERC Corp [Member] | Energy Related Derivative [Member] | Current Assets Held for Sale [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset		2
Gas Imbalance Payable [Member] | Energy Related Derivative [Member] | Current liabilities held for sale [Member]
Derivatives, Fair Value [Line Items]
Cumulative Amount of Fair Value Hedging Adjustment Included in the Carrying Amount of Hedged Item		1
Gas Imbalance Payable [Member] | CERC Corp [Member] | Energy Related Derivative [Member] | Current liabilities held for sale [Member]
Derivatives, Fair Value [Line Items]
Cumulative Amount of Fair Value Hedging Adjustment Included in the Carrying Amount of Hedged Item		1
Gas Imbalance Payable [Member] | Fair Value Hedging [Member] | Energy Related Derivative [Member] | Current liabilities held for sale [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability		0
Gas Imbalance Payable [Member] | Fair Value Hedging [Member] | CERC Corp [Member] | Energy Related Derivative [Member] | Current liabilities held for sale [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability		0
Discontinued Operations [Member]
Derivatives, Fair Value [Line Items]
Total amounts presented in the statements of income in which the effects of hedges are recorded		887	1,251
Discontinued Operations [Member] | CERC Corp [Member]
Derivatives, Fair Value [Line Items]
Total amounts presented in the statements of income in which the effects of hedges are recorded		$ 786	$ 1,171

[1] Gross amounts recognized include some derivative assets and liabilities that are not subject to master netting arrangements.

[2] The derivative assets and liabilities on the Registrant’s respective Condensed Consolidated Balance Sheets exclude accounts receivable or accounts payable that, should they exist, could be used as offsets to these balances in the event of a default.

[3] Derivative Assets and Derivative Liabilities include no material amounts related to physical forward transactions with Enable.

[4] Natural gas contracts are subject to master netting arrangements. This netting applies to all undisputed amounts due or past due. The net of total non-trading natural gas derivative assets and liabilities is detailed in the Offsetting of Natural Gas Derivative Assets and Liabilities table below.

[5] The fair value shown for natural gas contracts is comprised of derivative gross volumes totaling 2,126 Bcf or a net 232 Bcf long position and 2,226 Bcf or a net 374 Bcf long position as of March 31, 2020 and December 31, 2019, respectively. Certain natural gas contracts hedge basis risk only and lack a fixed price exposure.

[6] Derivative Assets and Derivative Liabilities include no material amounts related to physical forward transactions with Enable.

[7] Natural gas contracts are subject to master netting arrangements. This netting applies to all undisputed amounts due or past due The net of total non-trading natural gas derivative assets and liabilities is detailed in the Offsetting of Natural Gas Derivative Assets and Liabilities table below.

[8] The fair value shown for natural gas contracts is comprised of derivative gross volumes totaling 2,126 Bcf or a net 232 Bcf long position and 2,226 Bcf or a net 374 Bcf long position as of March 31, 2020 and December 31, 2019, respectively. Certain natural gas contracts hedge basis risk only and lack a fixed price exposure.

[9] Income statement impact associated with cash flow hedge activity is related to gains and losses reclassified from Accumulated other comprehensive income into income. Amounts are immaterial for each Registrant in the three months ended March 31, 2020 and 2019, respectively.