Long-term Debt (Details) (USD $) In Millions, unless otherwise specified	0 Months Ended		12 Months Ended
	Jun. 02, 2014	Mar. 03, 2014	Dec. 31, 2014		Dec. 31, 2013		Mar. 17, 2014
Debt Instrument [Line Items]
Other			$ (8)		$ (2)
Long-term Debt, Excluding Current Maturities			4,680		4,641
Long-term Debt, Current Maturities			372	[1]	354	[1]
Line of Credit Facility [Abstract]
Size of Credit Facility			300		300
Annual maturities of long-term debt [Abstract]
2015			0
2016			0
2017			0
2018			0
2019			0
Bonds General Mortgage Due 2044 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount							600
Debt Instrument, Interest Rate, Stated Percentage							4.50%
Secured Debt [Member] | Bonds Pollution Control Due2017 [Member]
Debt Instrument [Line Items]
Extinguishment of Debt, Amount	84	44
Debt Instrument, Redemption Price, Percentage of Principal Amount Redeemed	100.00%	101.00%
Debt Instrument, Interest Rate, Stated Percentage	4.25%	4.25%
Secured Debt [Member] | Bonds Pollution Control Due2027 [Member]
Debt Instrument [Line Items]
Debt Instrument, Redemption Price, Percentage of Principal Amount Redeemed		101.00%
Debt Instrument, Interest Rate, Stated Percentage		5.60%
Debt Instrument, Repurchase Amount		56
Transition And System Restoration Bonds [Member]
Annual maturities of long-term debt [Abstract]
2015			372
2016			391
2017			411
2018			434
2019			458
First mortgage bonds 9.15% due 2021
Debt Instrument [Line Items]
Long-term Debt, Gross, Noncurrent			102		102
Long-term Debt, Gross, Current			0	[1]	0	[1]
Debt Instrument, Interest Rate, Stated Percentage			9.15%
Annual maturities of long-term debt [Abstract]
Secured Debt			102
Replacement Fund Requirements			209
Sinking Fund Requirements			1.6
General mortgage bonds 2.25% to 6.95% due 2022 to 2044 (2)
Debt Instrument [Line Items]
Long-term Debt, Gross, Noncurrent			1,912	[2]	1,312	[2]
Long-term Debt, Gross, Current			0	[1],[2]	0	[1],[2]
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Minimum			2.25%
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Maximum			6.95%
Annual maturities of long-term debt [Abstract]
Secured Debt			2,400
Pollution control bonds 4.25% to 5.60% due 2017 to 2027(3)
Debt Instrument [Line Items]
Long-term Debt, Gross, Noncurrent			0	[3]	183	[3]
Long-term Debt, Gross, Current			0	[1],[3]	0	[1],[3]
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Minimum			4.25%
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Maximum			5.60%
System restoration bonds 1.833% to 4.243% due 2015 to 2022
Debt Instrument [Line Items]
Long-term Debt, Gross, Noncurrent			415		463
Long-term Debt, Gross, Current			48	[1]	47	[1]
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Minimum			1.833%
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Maximum			4.243%
Transition bonds 0.90% to 5.302% due 2015 to 2024
Debt Instrument [Line Items]
Long-term Debt, Gross, Noncurrent			2,259		2,583
Long-term Debt, Gross, Current			324	[1]	307	[1]
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Minimum			0.90%
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Maximum			5.302%
Revolving Credit Facility [Member]
Line of Credit Facility [Abstract]
Loans Outstanding			0		0
Line of Credit [Member]
Line of Credit Facility [Abstract]
Percentage on limitation of debt to total capitalization under covenant (in hundredths)			65.00%
Letter of Credit [Member]
Line of Credit Facility [Abstract]
Loans Outstanding			$ 4		$ 4
London Interbank Offered Rate (LIBOR) [Member] | Line of Credit [Member]
Line of Credit Facility [Abstract]
Line of Credit Facility, Interest Rate Description			1.125%

[1] Includes amounts due or scheduled to be paid within one year of the date noted.

[2] Debt issued as collateral is excluded from the financial statements because of the contingent nature of the obligation.

[3] These series of debt are collateralized by CenterPoint Houston’s general mortgage bonds.