Stock-Based Incentive Compensation Plans and Employee Benefit Plans Stock Based Incentive Compensation (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions		12 Months Ended
		Dec. 31, 2018		Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized for issuance under long-term incentive plans (in shares)		14,000
Employee Service Share-based Compensation, Aggregate Disclosures [Abstract]
Income tax benefit recognized related to LTIPs		$ 6		$ 8	$ 7
Actual tax benefit realized for tax deductions		$ 5		$ 6	$ 5
Performance Awards [Member]
Summary of nonvested shares [Roll Forward]
Nonvested, beginning of period (in shares)	[1]	3,627
Granted (in shares)	[1]	1,321
Forfeited or cancelled (in shares)	[1]	(721)
Vested and released to participants (in shares)	[1]	(409)
Nonvested, end of period (in shares)	[1]	3,818		3,627
Weighted average grant date fair value, nonvested, beginning of period (in dollars per share)	[1]	$ 22.15
Weighted average grant date fair values of awards granted (in dollars per share)		26.74	[1]	$ 26.64	$ 18.98
Weighted average grant date fair value, forfeited or cancelled (in dollars per share)	[1]	21.72
Weighted average grant date fair value, vested and released to participants (in dollars per share)	[1]	21.31
Weighted average grant date fair value, nonvested, end of period (in dollars per share)	[1]	$ 23.91		$ 22.15
Remaining average contractual life of nonvested shares outstanding (in years)	[1]	1 year
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Nonvested	[1],[2]	$ 57
Total intrinsic value of awards received by participants		12		$ 7	$ 7
Total grant date fair values of performance and stock awards which vested during the period		$ 9		$ 5	$ 7
Stock Awards [Member]
Summary of nonvested shares [Roll Forward]
Nonvested, beginning of period (in shares)		980
Granted (in shares)		409
Forfeited or cancelled (in shares)		(29)
Vested and released to participants (in shares)		(300)
Nonvested, end of period (in shares)		1,060		980
Weighted average grant date fair value, nonvested, beginning of period (in dollars per share)		$ 22.68
Weighted average grant date fair values of awards granted (in dollars per share)		26.62		$ 26.77	$ 19.24
Weighted average grant date fair value, forfeited or cancelled (in dollars per share)		25.31
Weighted average grant date fair value, vested and released to participants (in dollars per share)		22.84
Weighted average grant date fair value, nonvested, end of period (in dollars per share)		$ 24.08		$ 22.68
Remaining average contractual life of nonvested shares outstanding (in years)		1 year 1 month
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Nonvested	[2]	$ 30
Total intrinsic value of awards received by participants		9		$ 9	$ 6
Total grant date fair values of performance and stock awards which vested during the period		7		7	6
Performance and Stock Awards [Member]
Summary of nonvested shares [Roll Forward]
Unrecognized compensation cost related to non-vested performance and stock awards		$ 27
Weighted average period of recognition (in years)		1 year 8 months
Operation And Maintenance Expense [Member]
Employee Service Share-based Compensation, Aggregate Disclosures [Abstract]
LTIP compensation expense	[3]	$ 26		$ 21	$ 19

[1] Reflects maximum performance achievement.

[2] Reflects the impact of current expectations of achievement and stock price.

[3] Included in Operation and maintenance expense in CenterPoint Energy’s Statements of Consolidated Income and not capitalized as a part of Inventory or Property, Plant and Equipment.