Employee Benefit Plans and Equity Compensation Plan (Tables)

12 Months Ended

Dec. 31, 2023

Retirement Benefits [Abstract]

Schedule of Changes in Projected Benefit Obligations

The measurement date used to determine pension and other postretirement benefit obligations is December 31. Data related to the changes in the projected benefit obligation for pension benefits and the accumulated benefit obligation for other postretirement benefits are presented below.

	Pension Benefits						Other Postretirement Benefits
(millions)	2023			2022			2023			2022
Beginning balance	$	580		$	702		$	121		$	171
Service cost		8			8			1			1
Interest cost		33			21			8			6
Amendments		1			—			—			—
Actuarial (gain) loss		1			(105	)		1			(44	)
Benefits paid		(39	)		(46	)		(11	)		(13	)
Ending balance	$	584		$	580		$	120		$	121

Schedule of Assumptions Used to Determine Benefit Obligations

Significant assumptions used to determine the above benefit obligations are as follows:

	Pension Benefits						Other Postretirement Benefits
	2023			2022			2023			2022
Annual discount rate used to determine benefit obligation		5.39	%		5.69	%		5.42	%		5.70	%
Assumed annual rate of future salary increases for projected    benefit obligation		3.54	%		3.93	%	N/A			N/A
Crediting interest rate for cash balance plans		4.14	%		4.44	%	N/A			N/A

Schedule of Net Funded Status

	Pension Benefits					Other Postretirement Benefits
At December 31,	2023		2022			2023			2022
(millions)
Fair value of plan assets	$	588	$	561		$	—		$	—
Benefit obligation		584		580			120			121
Funded status	$	4	$	(19	)	$	(120	)	$	(121	)

Schedule of Amounts Recognized in Balance Sheet

Amounts recognized on the consolidated balance sheets were as follows:

	Pension Benefits					Other Postretirement Benefits
At December 31,	2023		2022			2023			2022
(millions)
Noncurrent assets	$	4	$	—		$	—		$	—
Current liability		—		—			(11	)		(11	)
Noncurrent liability		—		(19	)		(109	)		(110	)

Schedule of Amounts Recognized in AOCI

Amounts recognized in AOCI were as follows:

	Pension Benefits				Other Postretirement Benefits
At December 31,	2023		2022		2023			2022
(millions)
Net actuarial (gain) loss	$	2	$	3	$	(1	)	$	(1	)

Schedule of Amounts Recognized in Regulatory Assets

Amounts recognized in regulatory assets were as follows:

	Pension Benefits				Other Postretirement Benefits
At December 31,	2023		2022		2023			2022
(millions)
Net actuarial (gain) loss	$	126	$	164	$	(41	)	$	(46	)
Prior service cost		1		—		—			—
Total	$	127	$	164	$	(41	)	$	(46	)

Schedule of Changes in Fair Value of Plan Assets

Changes in Fair Value of Plan Assets

	Pension Benefits
At December 31,	2023			2022
(millions)
Beginning balance	$	561		$	768
Actual return (loss) on plan assets		66			(161	)
Benefits paid		(39	)		(46	)
Ending balance	$	588		$	561

Schedule of Fair Value Measurements By Category

At December 31, 2023 and 2022, fair value measurements, and the level within the fair value hierarchy in which the measurements fall, were as follows:

At December 31,	2023								2022
(millions)	Level 1		Level 2		Level 3		Total		Level 1		Level 2		Level 3		Total
Cash and cash equivalents	$	4	$	1	$	—	$	5	$	—	$	2	$	—	$	2
Corporate debt instruments		—		137		—		137		—		137		—		137
Government and other debt instruments		—		14		—		14		—		18		—		18
Total recorded at fair value	$	4	$	152	$	—	$	156	$	—	$	157	$	—	$	157
Assets recorded at NAV(1)
Commingled funds/collective trust funds								436								417
Total recorded at NAV							$	436							$	417
Total investments(2)							$	592							$	574

(1)These investments that are measured at fair value using the NAV per share (or its equivalent) as a practical expedient are not required to be categorized in the fair value hierarchy.

(2)Excludes net assets related to pending sales of securities of $1 million, net accrued income of $1 million, and includes net assets related to pending purchases of securities of $6 million at December 31, 2023. Excludes net assets related to pending sales of securities of $1 million, net accrued income of $1 million, and includes net assets related to pending purchases of securities of $15 million at December 31, 2022.

Schedule of Expected Benefit Payments

Expected Benefit Payments

(millions)	Pension Benefits		Other Postretirement Benefits
2024	$	47	$	11
2025		47		11
2026		45		11
2027		44		11
2028		46		11
2029 - 2033		236		55

Components of Net Periodic Benefit Cost

Components of Net Periodic Benefit (Credit) Cost

	Pension Benefits									Other Postretirement Benefits
Year Ended December 31,	2023			2022			2021			2023			2022		2021
(millions)
Service cost	$	8		$	8		$	9		$	1		$	1	$	1
Interest cost		33			21			20			8			6		6
Expected return on assets		(34	)		(49	)		(48	)		—			—		—
Amortization of actuarial losses (gains)		12			1			6			(4	)		—		—
Net periodic benefit (credit) cost	$	19		$	(19	)	$	(13	)	$	5		$	7	$	7

Schedule of Defined Benefit Plan Amounts Recognized in Other Comprehensive Income (Loss)

Other changes in plan assets and benefit obligations recognized in other comprehensive income (net of tax) were as follows:

	Pension Benefits								Other Postretirement Benefits
Year Ended December 31,	2023			2022		2021			2023		2022			2021
(millions)
Current year actuarial (gain) loss	$	(1	)	$	2	$	(3	)	$	—	$	(1	)	$	—
Total recognized in other comprehensive income	$	(1	)	$	2	$	(3	)	$	—	$	(1	)	$	—

Schedule of Defined Benefit Plan Amounts Recognized in Regulatory Assets

Other changes in plan assets and benefit obligations recognized in regulatory assets were as follows:

	Pension Benefits									Other Postretirement Benefits
Year Ended December 31,	2023			2022			2021			2023		2022			2021
(millions)
Current year actuarial (gain) loss	$	(27	)	$	95		$	(39	)	$	2	$	(41	)	$	(6	)
Amortization of actuarial gain (loss)		(11	)		(1	)		(5	)		3		—			—
Current year prior service cost		1			—			—			—		—			—
Total recognized in regulatory assets	$	(37	)	$	94		$	(44	)	$	5	$	(41	)	$	(6	)

Schedule of Assumptions Used in Determining Net Periodic Benefit Cost

Significant assumptions used in determining net periodic benefit cost:

	Pension Benefits									Other Postretirement Benefits
Year Ended December 31,	2023			2022			2021			2023			2022			2021
Discount rate		5.69	%		3.06	%		2.73	%		5.70	%		3.11	%		2.80	%
Expected return on plan assets		7.00	%		7.00	%		7.00	%	n/a			n/a			n/a
Rate of compensation increase		3.93	%		3.71	%		4.52	%	n/a			n/a			n/a
Crediting interest rate for cash balance plans		4.44	%		1.81	%		1.93	%	n/a			n/a			n/a
Health care cost trend rate											7.00	%		6.25	%		6.25	%
Ultimate health care cost trend rate											5.00	%		5.00	%		5.00	%
Year achieved										2030			2026-2027			2025-2026