Stock-Based Incentive Compensation Plans and Employee Benefit Plans (Tables)

12 Months Ended

Dec. 31, 2018

Defined Benefit Plan Disclosure [Line Items]

Schedule of Compensation Cost for Share-based Payment Arrangements, Allocation of Share-based Compensation Costs by Plan [Table Text Block]

The following table summarizes CenterPoint Energy’s expenses related to LTIPs for 2018, 2017 and 2016:

	Year Ended December 31,
	2018		2017		2016
	(in millions)
LTIP Compensation expense (1)	$	26	$	21	$	19
Income tax benefit recognized	6		8		7
Actual tax benefit realized for tax deductions	5		6		5

(1) 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.

Share-Based Compensation, Activity [Table Text Block]

The following tables summarize CenterPoint Energy’s LTIP activity for 2018:

	Year Ended December 31, 2018
	Shares (Thousands)		Weighted-Average Grant Date Fair Value		Remaining Average Contractual Life (Years)	Aggregate Intrinsic Value (2) (Millions)
Performance Awards(1)
Outstanding and non-vested as of December 31, 2017	3,627		$	22.15
Granted	1,321		26.74
Forfeited or canceled	(721	)	21.72
Vested and released to participants	(409	)	21.31
Outstanding and non-vested as of December 31, 2018	3,818		$	23.91	1	$	57
Stock Awards
Outstanding and non-vested as of December 31, 2017	980		$	22.68
Granted	409		26.62
Forfeited or canceled	(29	)	25.31
Vested and released to participants	(300	)	22.84
Outstanding and non-vested as of December 31, 2018	1,060		$	24.08	1.1	$	30

(1) Reflects maximum performance achievement.

(2) Reflects the impact of current expectations of achievement and stock price.

Share-Based Compensation Arrangement By Award, Weighted Average Grant Date Fair Value, Grant Date Intrinsic Value, and Vested Grant Date Fair Value [Table Text Block]

The weighted average grant date fair values per unit of awards granted were as follows for 2018, 2017 and 2016:

	Year Ended December 31,
	2018		2017		2016
	(In millions, except for per unit amounts)
Performance Awards
Weighted-average grant date fair value per unit of awards granted	$	26.74	$	26.64	$	18.98
Total intrinsic value of awards received by participants	12		7		7
Vested grant date fair value	9		5		7
Stock Awards
Weighted-average grant date fair value per unit of awards granted	$	26.62	$	26.77	$	19.24
Total intrinsic value of awards received by participants	9		9		6
Vested grant date fair value	7		7		6

Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]

Amounts recognized in accumulated other comprehensive loss (gain) consist of the following:

	December 31,
	2018								2017
	Pension Benefits		Postretirement Benefits						Pension Benefits		Postretirement Benefits
	CenterPoint Energy		CenterPoint Energy			CERC			CenterPoint Energy		CenterPoint Energy			CERC
	(in millions)
Unrecognized actuarial loss (gain)	$	109	$	(7	)	$	(3	)	$	94	$	(8	)	$	(2	)
Unrecognized prior service cost	1		5			5			1		6			6
Deferred tax benefit (1)	—		—			(9		)	—		—			(11		)
Net amount recognized in accumulated other comprehensive loss (gain)	$	110	$	(2	)	$	(7	)	$	95	$	(2	)	$	(7	)

(1) CenterPoint Energy’s and CERC’s postretirement benefit obligation is reduced by the impact of previously non-taxable government subsidies under the Medicare Prescription Drug Act. Because the subsidies were non-taxable, the temporary difference used in measuring the deferred tax impact was determined on the unrecognized losses excluding such subsidies.

Changes in accumulated comprehensive income (loss) are as follows:

	Year Ended December 31,
	2018									2017
	CenterPoint Energy			Houston Electric			CERC			CenterPoint Energy			Houston Electric			CERC
	(in millions)
Beginning Balance	$	(68	)	$	—		$	6		$	(71	)	$	1		$	3
Other comprehensive income (loss) before reclassifications:
Remeasurement of pension and other postretirement plans	(19		)	—			1			4			—			7
Deferred loss from interest rate derivatives (1)	(19		)	(18		)	(1		)	(5		)	(1		)	(2		)
Amounts reclassified from accumulated other comprehensive loss:
Prior service cost (2)	1			—			1			1			—			1
Actuarial losses (2)	6			—			—			7			—			—
Tax benefit (expense)	6			4			(1		)	(4		)	—			(3		)
Net current period other comprehensive income (loss)	(25		)	(14		)	—			3			(1		)	3
Adoption of ASU 2018-02	(15		)	—			(1		)	—			—			—
Ending Balance	$	(108	)	$	(14	)	$	5		$	(68	)	$	—		$	6

(1) Gains and losses are reclassified from Accumulated other comprehensive income into income when the hedged transactions affect earnings. The reclassification amounts are included in Interest and other finance charges in each of the Registrant’s respective Statements of Consolidated Income. Amounts are less than $1 million for each of the years ended December 31, 2018 and 2017, respectively.

(2) Amounts are included in the computation of net periodic cost and are reflected in Other, net in each of the Registrants’ respective Statements of Consolidated Income.

Schedule of Defined Benefit Plan Amounts Recognized in Other Comprehensive Income (Loss) [Table Text Block]

The changes in plan assets and benefit obligations recognized in other comprehensive income during 2018 are as follows:

	Pension Benefits			Postretirement Benefits
	CenterPoint Energy			CenterPoint Energy		CERC
	(in millions)
Net loss (gain)	$	22		$	—	$	(1	)
Amortization of net loss	(6		)	—		—
Amortization of prior service cost	(1		)	—		(1		)
Total recognized in comprehensive income	$	15		$	—	$	(2	)
Total expense recognized in net periodic costs and Other comprehensive income	$	76		$	5	$	3

Benefit Plan Contributions [Table Text Block]

The Registrants made the following contributions in 2018 and expect to make the following minimum contributions in 2019 to the indicated benefit plans below:

	Contributions in 2018						Expected Minimum Contributions in 2019
	CenterPoint Energy		Houston Electric		CERC		CenterPoint Energy		Houston Electric		CERC
	(in millions)
Qualified pension plan	$	60	$	—	$	—	$	86	$	—	$	—
Non-qualified pension plan	9		—		—		7		—		—
Postretirement benefit plan	14		9		4		17		10		4

Schedule of Expected Benefit Payments [Table Text Block]

The following benefit payments are expected to be paid by the pension and postretirement benefit plans:

	Pension Benefits		Postretirement Benefits
	CenterPoint Energy		CenterPoint Energy		Houston Electric		CERC
	(in millions)
2019	$	141	$	16	$	9	$	5
2020	146		19		10		6
2021	154		20		11		6
2022	155		21		11		7
2023	156		22		12		7
2024-2028	759		116		61		37

Defined Contribution Plan Disclosures [Table Text Block]

CenterPoint Energy allocates to Houston Electric and CERC the savings plan benefit expense related to their respective employees. The following table summarizes the Registrants’ savings plan benefit expense for 2018, 2017 and 2016:

	Year Ended December 31,
	2018						2017						2016
	CenterPoint Energy		Houston Electric		CERC		CenterPoint Energy		Houston Electric		CERC		CenterPoint Energy		Houston Electric		CERC
	(in millions)
Savings plan benefit  expenses	$	43	$	17	$	18	$	41	$	17	$	17	$	38	$	15	$	16

Other Benefit Plans [Table Text Block]

Expenses related to other benefit plans were recorded as follows:

	Year Ended December 31,
	2018						2017						2016
	CenterPoint Energy		Houston Electric		CERC		CenterPoint Energy		Houston Electric		CERC		CenterPoint Energy		Houston Electric		CERC
	(in millions)
Postemployment benefits	$	3	$	4	$	1	$	6	$	1	$	4	$	5	$	3	$	3
Deferred compensation plans	3		1		—		3		1		—		3		1		—

Amounts related to other benefit plans were included in Benefit Obligations in the Registrants’ accompanying Consolidated Balance Sheets as follows:

	December 31, 2018						December 31, 2017
	CenterPoint Energy		Houston Electric		CERC		CenterPoint Energy		Houston Electric		CERC
	(in millions)
Postemployment benefits	$	11	$	3	$	7	$	20	$	3	$	14
Deferred compensation plans	42		9		3		45		10		3
Split-dollar life insurance arrangements	36		1		—		39		1		—

Other Employee Matters [Table Text Block]

As of December 31, 2018, the Registrants’ employees were covered by collective bargaining agreements as follows:

		Percentage of Employees Covered
	Agreement Expiration	CenterPoint Energy		Houston Electric		CERC
IBEW Local 66	May 2020	18	%	51	%	—
OPEIU Local 12 and Mankato	March and May 2021	3	%	—		3	%
Gas Workers Union Local 340	April 2020	6	%	—		12	%
IBEW Local 949	December 2020	3	%	—		7	%
USW Locals 13-227 and 13-1	June and July 2022	5	%	—		11	%
Total		35	%	51	%	33	%

Pension Plan [Member]

Defined Benefit Plan Disclosure [Line Items]

Schedule of Net Benefit Costs [Table Text Block]

CenterPoint Energy’s net periodic cost includes the following components relating to pension, including the non-qualified benefit restoration plan:

	Year Ended December 31,
	2018			2017			2016
	(in millions)
Service cost (1)	$	37		$	36		$	38
Interest cost (2)	79			89			93
Expected return on plan assets (2)	(107		)	(97		)	(101		)
Amortization of prior service cost (2)	9			9			9
Amortization of net loss (2)	43			58			63
Net periodic cost	$	61		$	95		$	102

(1) Amounts presented in the table above are included in Operation and maintenance expense in CenterPoint Energy’s Statements of Consolidated Income, net of regulatory deferrals and amounts capitalized. See Note 2(r).

(2) Amounts presented in the table above are included in Other, net in CenterPoint Energy’s Statements of Consolidated Income, net of regulatory deferrals. See Note 2(r).

Schedule of Assumptions Used [Table Text Block]

CenterPoint Energy used the following assumptions to determine net periodic cost relating to pension benefits:

	Year Ended December 31,
	2018		2017		2016
Discount rate	3.65	%	4.15	%	4.40	%
Expected return on plan assets	6.00		6.00		6.25
Rate of increase in compensation levels	4.45		4.50		4.15

Schedule of Net Pension and Post-retirement Benefit Costs [Table Text Block]

The following table summarizes changes in the benefit obligation, plan assets, the amounts recognized in the Consolidated Balance Sheets as well as the key assumptions of CenterPoint Energy’s pension plans. The measurement dates for plan assets and obligations were December 31, 2018 and 2017.

	December 31,
	2018			2017
	(in millions, except for actuarial assumptions)
Change in Benefit Obligation
Benefit obligation, beginning of year	$	2,225		$	2,197
Service cost	37			36
Interest cost	79			89
Benefits paid	(201		)	(168		)
Actuarial (gain) loss (1)	(127		)	71
Benefit obligation, end of year	2,013			2,225
Change in Plan Assets
Fair value of plan assets, beginning of year	1,801			1,656
Employer contributions	69			48
Benefits paid	(201		)	(168		)
Actual investment return	(153		)	265
Fair value of plan assets, end of year	1,516			1,801
Funded status, end of year	$	(497	)	$	(424	)

	December 31,
	2018			2017
	(in millions, except for actuarial assumptions)
Amounts Recognized in Balance Sheets
Current liabilities-other	$	(7	)	$	(7	)
Other liabilities-benefit obligations	(490		)	(417		)
Net liability, end of year	$	(497	)	$	(424	)
Actuarial Assumptions
Discount rate (2)	4.35		%	3.65		%
Expected return on plan assets (3)	6.00			6.00
Rate of increase in compensation levels	4.60			4.45
Interest crediting rate	3.75			3.75

(1) Significant sources of gain for 2018 include the increase in discount rate from 3.65% to 4.35% and the mortality projection scale change from MP2017 to MP2018. For 2017, the significant source of loss was the decrease in the discount rate from 4.15% to 3.65%.

(2) The discount rate assumption was determined by matching the projected cash flows of CenterPoint Energy’s plans against a hypothetical yield curve of high-quality corporate bonds represented by a series of annualized individual discount rates from one-half to 99 years.

(3) The expected rate of return assumption was developed using the targeted asset allocation of CenterPoint Energy’s plans and the expected return for each asset class.

Schedule of Accumulated Benefit Obligations in Excess of Fair Value of Plan Assets [Table Text Block]

The following table displays pension benefits related to CenterPoint Energy’s pension plans that have accumulated benefit obligations in excess of plan assets:

	December 31,
	2018				2017
	Pension (Qualified)		Pension (Non-qualified)		Pension (Qualified)		Pension (Non-qualified)
	(in millions)
Accumulated benefit obligation	$	1,930	$	61	$	2,090	$	74
Projected benefit obligation	1,952		61		2,151		74
Fair value of plan assets	1,516		—		1,801		—

Target Allocation of Plan Assets [Table Text Block]

As part of the investment strategy discussed above, CenterPoint Energy maintained the following weighted average allocation targets for its pension plans as of December 31, 2018:

U.S. equity	12 - 28%
International developed market equity	7 - 17%
Emerging market equity	5 - 11%
Fixed income	55 - 65%
Cash	0 - 2%

Schedule of Allocation of Plan Assets [Table Text Block]

The following tables set forth by level, within the fair value hierarchy (see Note 10), CenterPoint Energy’s pension plan assets at fair value as of December 31, 2018 and 2017:

	Fair Value Measurements as of December 31,
	2018										2017
	(Level 1)			(Level 2)		(Level 3)		Total			(Level 1)			(Level 2)		(Level 3)		Total
	(in millions)
Cash	$	19		$	—	$	—	$	19		$	18		$	—	$	—	$	18
Corporate bonds:
Investment grade or above	—			368		—		368			—			432		—		432
Equity securities:
U.S. companies	60			—		—		60			76			—		—		76
Cash received as collateral from securities lending	77			—		—		77			76			—		—		76
U.S. treasuries	196			—		—		196			67			—		—		67
Mortgage backed securities	—			6		—		6			—			8		—		8
Asset backed securities	—			1		—		1			—			1		—		1
Municipal bonds	—			27		—		27			—			47		—		47
Mutual funds (2)	167			—		—		167			211			—		—		211
International government bonds	—			16		—		16			—			17		—		17
Obligation to return cash received as collateral from securities lending	(77		)	—		—		(77		)	(76		)	—		—		(76		)
Total investments at fair value	$	442		$	418	$	—	860			$	372		$	505	$	—	877
Investments measured by net asset value per share or its equivalent (1) (2)								656										924
Total Investments								$	1,516									$	1,801

(1) Represents investments in common collective trust funds.

(2) The amounts invested in mutual funds and common collective trust funds were allocated as follows:

	As of December 31,
	2018				2017
	Mutual Funds		Common Collective Trust Funds		Mutual Funds		Common Collective Trust Funds
International equities	51	%	37	%	57	%	34	%
Emerging market equities	34	%	4	%	30	%	5	%
U.S. equities	15	%	5	%	13	%	6	%
Fixed income	—		54	%	—		55	%

Postretirement Benefits [Member]

Defined Benefit Plan Disclosure [Line Items]

Schedule of Net Benefit Costs [Table Text Block]

Postretirement benefits are accrued over the active service period of employees. The net postretirement benefit cost includes the following components:

	Year Ended December 31,
	2018									2017									2016
	CenterPoint Energy			Houston Electric			CERC			CenterPoint Energy			Houston Electric			CERC			CenterPoint Energy			Houston Electric			CERC
	(in millions)
Service cost (1)	$	2		$	—		$	1		$	2		$	1		$	1		$	2		$	1		$	1
Interest cost (2)	13			8			4			16			9			5			16			10			4
Expected return on plan assets (2)	(5		)	(4		)	(1		)	(5		)	(4		)	(1		)	(6		)	(5		)	(1		)
Amortization of prior service cost (credit) (2)	(5		)	(5		)	1			(5		)	(6		)	1			(3		)	(4		)	—
Amortization of net loss (2)	—			—			—			—			—			—			1			1			1
Curtailment (3)	—			—			—			—			—			—			(5		)	(4		)	(1		)
Net postretirement benefit cost (credit)	$	5		$	(1	)	$	5		$	8		$	—		$	6		$	5		$	(1	)	$	4

(1) Amounts presented in the table above are included in Operation and maintenance expense in CenterPoint Energy’s Statements of Consolidated Income, net of regulatory deferrals and amounts capitalized. See Note 2(r).

(2) Amounts presented in the table above are included in Other, net in each of the Registrants’ respective Statements of Consolidated Income, net of regulatory deferrals. See Note 2(r).

(3) A curtailment gain or loss is required when the expected future services of a significant number of current employees are reduced or eliminated for the accrual of benefits. During 2016, postretirement healthcare benefits were amended resulting in a net curtailment gain of $5 million. In May 2016, Houston Electric entered into a renegotiated collective bargaining agreement with the IBEW Local Union 66 that provides that for Houston Electric bargaining unit employees covered under the agreement who retire on or after January 1, 2017, retiree medical and prescription drug coverage will be provided exclusively through the NECA/IBEW Family Medical Care Plan in exchange for the payment of monthly premiums as determined under the agreement. As a result, the accrued postretirement benefits related to such future CenterPoint Energy and Houston Electric union retirees were eliminated. Houston Electric recognized a curtailment gain of $3 million as an accelerated recognition of the prior service credit that would otherwise be recognized in future periods for the postretirement plan. CenterPoint Energy also recognized an additional curtailment gain of $2 million in October 2016 related to other amendments in the postretirement plan.

Schedule of Assumptions Used [Table Text Block]

The following assumptions were used to determine net periodic cost relating to postretirement benefits:

	Year Ended December 31,
	2018						2017						2016
	CenterPoint Energy		Houston Electric		CERC		CenterPoint Energy		Houston Electric		CERC		CenterPoint Energy		Houston Electric		CERC
Discount rate	3.60	%	3.60	%	3.60	%	4.15	%	4.15	%	4.15	%	4.35	%	4.35	%	4.35	%
Expected return on plan assets	4.55		4.75		3.85		4.50		4.75		3.60		4.80		5.00		3.95

Schedule of Net Pension and Post-retirement Benefit Costs [Table Text Block]

The following table summarizes changes in the benefit obligation, plan assets, the amounts recognized in consolidated balance sheets and the key assumptions of the postretirement plans. The measurement dates for plan assets and benefit obligations were December 31, 2018 and 2017.

	December 31,
	2018									2017
	CenterPoint Energy			Houston Electric			CERC			CenterPoint Energy			Houston Electric			CERC
	(in millions)
Change in Benefit Obligation
Benefit obligation, beginning of year	$	386		$	225		$	109		$	383		$	217		$	115
Service cost	2			—			1			2			1			1
Interest cost	13			8			4			16			9			5
Participant contributions	7			2			4			7			2			3
Benefits paid	(25		)	(13		)	(9		)	(26		)	(14		)	(9		)
Actuarial (gain) loss (1)	(52		)	(56		)	1			4			10			(6		)
Benefit obligation, end of year	331			166			110			386			225			109
Change in Plan Assets
Fair value of plan assets, beginning of year	120			93			26			113			88			25
Employer contributions	14			9			4			16			10			5
Participant contributions	7			2			4			7			2			3
Benefits paid	(25		)	(13		)	(9		)	(26		)	(14		)	(9		)
Actual investment return	(2		)	(2		)	—			10			7			2
Fair value of plan assets, end of year	114			89			25			120			93			26
Funded status, end of year	$	(217	)	$	(77	)	$	(85	)	$	(266	)	$	(132	)	$	(83	)
Amounts Recognized in Balance Sheets
Current liabilities-other	$	(6	)	$	—		$	(3	)	$	(6	)	$	—		$	(4	)
Other liabilities-benefit obligations	(211		)	(77		)	(82		)	(260		)	(132		)	(79		)
Net liability, end of year	$	(217	)	$	(77	)	$	(85	)	$	(266	)	$	(132	)	$	(83	)
Actuarial Assumptions
Discount rate (2)	4.35		%	4.35		%	4.35		%	3.60		%	3.60		%	3.60		%
Expected return on plan assets (3)	4.60			4.70			4.15			4.55			4.75			3.85
Medical cost trend rate assumed for the next year - Pre-65	5.95			5.95			5.95			6.15			6.15			6.15
Medical/prescription drug cost trend rate assumed for the next year - Post-65	28.60			28.60			28.60			23.85			23.85			23.85
Prescription drug cost trend rate assumed for the next year - Pre-65	9.20			9.20			9.20			9.85			9.85			9.85
Rate to which the cost trend rate is assumed to decline (the ultimate trend rate)	4.50			4.50			4.50			4.50			4.50			4.50
Year that the cost trend rates reach the ultimate trend rate - Pre-65	2026			2026			2026			2026			2026			2026
Year that the cost trend rates reach the ultimate trend rate - Post-65	2027			2027			2027			2024			2024			2024

(1) Significant sources of gain for 2018 include the increase in the discount rate from 3.60% to 4.35%, favorable benefit claims experience and cost trend rates in addition to the change in mortality projection scale from MP2017 to MP2018.

(2) The discount rate assumption was determined by matching the projected cash flows of the plans against a hypothetical yield curve of high-quality corporate bonds represented by a series of annualized individual discount rates from one-half to 99 years.

(3) The expected rate of return assumption was developed using the targeted asset allocation of the plans and the expected return for each asset class.

Target Allocation of Plan Assets [Table Text Block]

As part of the investment strategy discussed above, the Registrants maintained the following weighted average allocation targets for the postretirement plans as of December 31, 2018:

	CenterPoint Energy	Houston Electric	CERC
U.S. equity	13 - 23%	13 - 23%	15 - 25%
International developed market equity	3 - 13%	3 - 13%	2 - 12%
Fixed income	69 - 79%	69 - 79%	68 - 78%
Cash	0 - 2%	0 - 2%	0 - 2%

Schedule of Allocation of Plan Assets [Table Text Block]

The following table presents mutual funds by level, within the fair value hierarchy, the Registrants’ postretirement plan assets at fair value as of December 31, 2018 and 2017:

	Fair Value Measurements as of December 31,
	2018								2017
	Mutual Funds
	(Level 1)		(Level 2)		(Level 3)		Total		(Level 1)		(Level 2)		(Level 3)		Total
	(in millions)
CenterPoint Energy	$	114	$	—	$	—	$	114	$	120	$	—	$	—	$	120
Houston Electric	89		—		—		89		93		—		—		93
CERC	25		—		—		25		26		—		—		26

The amounts invested in mutual funds were allocated as follows:

	As of December 31,
	2018						2017
	CenterPoint Energy		Houston Electric		CERC		CenterPoint Energy		Houston Electric		CERC
Fixed income	74	%	74	%	73	%	74	%	74	%	71	%
U.S. equities	19	%	19	%	21	%	18	%	18	%	21	%
International equities	7	%	7	%	6	%	8	%	8	%	8	%