Employee Benefit Plans (Tables)

12 Months Ended

Dec. 31, 2016

Compensation and Retirement Disclosure [Abstract]

Changes in benefit obligations and plan assets [Table Text Block]

The following table presents the changes in benefit obligations and plan assets for pension benefits and other postretirement benefits for the years indicated:

	Pension Benefits						Other Postretirement Benefits
	2016			2015			2016			2015
	(Millions)
Change in benefit obligation:
Benefit obligation at beginning of year	$	1,464		$	1,544		$	202		$	233
Service cost	54			59			1			2
Interest cost	62			58			8			9
Plan participants’ contributions	—			—			2			2
Benefits paid	(130		)	(101		)	(15		)	(13		)
Actuarial loss (gain)	20			(91		)	(1		)	(31		)
Settlements	(4		)	(5		)	—			—
Net increase (decrease) in benefit obligation	2			(80		)	(5		)	(31		)
Benefit obligation at end of year	1,466			1,464			197			202
Change in plan assets:
Fair value of plan assets at beginning of year	1,241			1,293			201			208
Actual return on plan assets	82			(11		)	13			(1		)
Employer contributions	65			65			7			5
Plan participants’ contributions	—			—			2			2
Benefits paid	(130		)	(101		)	(15		)	(13		)
Settlements	(4		)	(5		)	—			—
Net increase (decrease) in fair value of plan assets	13			(52		)	7			(7		)
Fair value of plan assets at end of year	1,254			1,241			208			201
Funded status — overfunded (underfunded)	$	(212	)	$	(223	)	$	11		$	(1	)
Accumulated benefit obligation	$	1,440		$	1,432

Overfunded (underfunded) status of our pension plans and other postretirement benefit plans [Table Text Block]

The overfunded (underfunded) status of our pension plans and other postretirement benefit plans presented in the previous table are recognized in the Consolidated Balance Sheet within the following accounts:

	December 31,
	2016			2015
	(Millions)
Underfunded pension plans:
Current liabilities	$	(2	)	$	(2	)
Noncurrent liabilities	(210		)	(221		)
Overfunded (underfunded) other postretirement benefit plans:
Current liabilities	(7		)	(7		)
Noncurrent assets (liabilities)	18			6

Pre-tax amounts not yet recognized in net periodic benefit cost [Table Text Block]

Pre-tax amounts not yet recognized in Net periodic benefit cost at December 31 are as follows:

	Pension Benefits						Other Postretirement Benefits
	2016			2015			2016			2015
	(Millions)
Amounts included in Accumulated other comprehensive income (loss):
Prior service credit	$	—		$	—		$	5		$	11
Net actuarial loss	(535		)	(544		)	(18		)	(18		)
Amounts included in regulatory liabilities associated with Transco and Northwest Pipeline:
Prior service credit	N/A			N/A			$	10		$	19
Net actuarial gain	N/A			N/A			8			6

Schedule of Net Benefit Costs [Table Text Block]

Net periodic benefit cost for the years ended December 31 consist of the following:

	Pension Benefits									Other Postretirement  Benefits
	2016			2015			2014			2016			2015			2014
	(Millions)
Components of net periodic benefit cost:
Service cost	$	54		$	59		$	40		$	1		$	2		$	2
Interest cost	62			58			62			8			9			10
Expected return on plan assets	(85		)	(75		)	(76		)	(12		)	(12		)	(12		)
Amortization of prior service credit	—			—			—			(15		)	(17		)	(20		)
Amortization of net actuarial loss	30			42			39			—			2			—
Net actuarial (gain) loss from settlements and curtailments	2			2			1			—			—			(1		)
Reclassification to regulatory liability	—			—			—			4			3			4
Net periodic benefit cost	$	63		$	86		$	66		$	(14	)	$	(13	)	$	(17	)

Other changes in plan assets and benefit obligations recognized in other comprehensive income (loss) [Table Text Block]

Other changes in plan assets and benefit obligations recognized in Other comprehensive income (loss) before taxes for the years ended December 31 consist of the following:

	Pension Benefits								Other Postretirement  Benefits
	2016			2015		2014			2016			2015			2014
	(Millions)
Other changes in plan assets and benefit obligations recognized in Other comprehensive income (loss):
Net actuarial gain (loss)	$	(23	)	$	5	$	(142	)	$	—		$	8		$	(18	)
Prior service (cost) credit	—			—		—			—			—			(1		)
Amortization of prior service credit	—			—		—			(6		)	(6		)	(8		)
Amortization of net actuarial loss	30			42		39			—			2			—
Loss from settlements and curtailments	2			2		1			—			—			1
Other changes in plan assets and benefit obligations recognized in Other comprehensive income (loss)	$	9		$	49	$	(102	)	$	(6	)	$	4		$	(26	)

Schedule of Regulatory Assets / Liabilities [Table Text Block]

Other changes in plan assets and benefit obligations for our other postretirement benefit plans associated with Transco and Northwest Pipeline are recognized in regulatory assets/liabilities.Amounts recognized in regulatory assets/ liabilities for the years ended December 31 consist of the following:

	2016			2015			2014
	(Millions)
Other changes in plan assets and benefit obligations recognized in regulatory (assets) liabilities:
Net actuarial gain (loss)	$	2		$	10		$	(2	)
Amortization of prior service credit	(9		)	(11		)	(12		)

Pre-tax amounts expected to be amortized in net periodic benefit cost [Table Text Block]

Pre-tax amounts expected to be amortized in Net periodic benefit cost in 2017 are as follows:

	Pension Benefits		Other Postretirement Benefits
	(Millions)
Amounts included in Accumulated other comprehensive income (loss):
Prior service credit	$	—	$	(5	)
Net actuarial loss	28		—
Amounts included in regulatory liabilities associated with Transco and Northwest Pipeline:
Prior service credit	N/A		$	(8	)
Net actuarial loss	N/A		—

Schedule of Assumptions Used [Table Text Block]

The weighted-average assumptions utilized to determine benefit obligations as of December 31 are as follows:

	Pension Benefits				Other Postretirement Benefits
	2016		2015		2016		2015
Discount rate	4.17	%	4.38	%	4.27	%	4.50	%
Rate of compensation increase	4.87		4.88		N/A		N/A

The weighted-average assumptions utilized to determine Net periodic benefit cost for the years ended December 31 are as follows:

	Pension Benefits						Other Postretirement  Benefits
	2016		2015		2014		2016		2015		2014
Discount rate	4.37	%	3.96	%	4.68	%	4.50	%	4.12	%	4.80	%
Expected long-term rate of return on plan assets	6.85		6.38		6.85		6.11		5.70		6.11
Rate of compensation increase	4.88		4.62		4.56		N/A		N/A		N/A

One percentage point change in assumed health care cost trend rates effects [Table Text Block]

A one-percentage-point change in assumed health care cost trend rates would have the following effects:

	Point increase		Point decrease
	(Millions)
Effect on total of service and interest cost components	$	—	$	—
Effect on other postretirement benefit obligation	6		(5		)

Fair values of plan assets [Table Text Block]

The fair values of our pension plan assets at December 31, 2016 and 2015 by asset class are as follows:

	2016
	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Total
	(Millions)
Pension assets:
Cash management fund	$	14	$	—	$	—	$	14
Equity securities:
U.S. large cap	87		—		—		87
U.S. small cap	77		—		—		77
Fixed income securities (1):
U.S. Treasury securities	68		—		—		68
Government and municipal bonds	—		10		—		10
Mortgage and asset-backed securities	—		80		—		80
Corporate bonds	—		148		—		148
Insurance company investment contracts and other	—		5		—		5
	$	246	$	243	$	—	489
Commingled investment funds measured at net asset value practical expedient (3):
Equities — U.S. large cap							369
Equities — International small cap							27
Equities — International emerging markets							50
Equities — International developed markets							149
Fixed income — U.S. long duration							88
Fixed income — Corporate bonds							82
Total assets at fair value at December 31, 2016							$	1,254

	2015
	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Total
	(Millions)
Pension assets:
Cash management fund	$	8	$	—	$	—	$	8
Equity securities:
U.S. large cap	83		—		—		83
U.S. small cap	64		—		—		64
Fixed income securities (1):
U.S. Treasury securities	65		—		—		65
Government and municipal bonds	—		8		—		8
Mortgage and asset-backed securities	—		87		—		87
Corporate bonds	—		145		—		145
Insurance company investment contracts and other	—		5		—		5
	$	220	$	245	$	—	465
Commingled investment funds measured at net asset value practical expedient (3):
Equities — U.S. large cap							367
Equities — International small cap							27
Equities — International emerging markets							50
Equities — International developed markets							153
Fixed income — U.S. long duration							95
Fixed income — Corporate bonds							84
Total assets at fair value at December 31, 2015							$	1,241

The fair values of our other postretirement benefits plan assets at December 31, 2016 and 2015 by asset class are as follows:

	2016
	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Total
	(Millions)
Other postretirement benefit assets:
Cash management funds	$	11	$	—	$	—	$	11
Equity securities:
U.S. large cap	24		—		—		24
U.S. small cap	15		—		—		15
International developed markets large cap growth	—		5		—		5
Fixed income securities (2):
U.S. Treasury securities	7		—		—		7
Government and municipal bonds	—		1		—		1
Mortgage and asset-backed securities	—		8		—		8
Corporate bonds	—		15		—		15
Mutual fund — Municipal bonds	42		—		—		42
	$	99	$	29	$	—	128
Commingled investment funds measured at net asset value practical expedient (3):
Equities — U.S. large cap							38
Equities — International small cap							3
Equities — International emerging markets							5
Equities — International developed markets							16
Fixed income — U.S. long duration							9
Fixed income — Corporate bonds							9
Total assets at fair value at December 31, 2016							$	208

	2015
	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Total
	(Millions)
Other postretirement benefit assets:
Cash management funds	$	11	$	—	$	—	$	11
Equity securities:
U.S. large cap	37		—		—		37
U.S. small cap	20		—		—		20
International developed markets large cap growth	1		9		—		10
Emerging markets growth	—		1		—		1
Fixed income securities (2):
U.S. Treasury securities	7		—		—		7
Government and municipal bonds	—		12		—		12
Mortgage and asset-backed securities	—		9		—		9
Corporate bonds	—		15		—		15
	$	76	$	46	$	—	122
Commingled investment funds measured at net asset value practical expedient (3):
Equities — U.S. large cap							37
Equities — International small cap							3
Equities — International emerging markets							5
Equities — International developed markets							16
Fixed income — U.S. long duration							10
Fixed income — Corporate bonds							8
Total assets at fair value at December 31, 2015							$	201

____________

(1) The weighted-average credit quality rating of the pension assets fixed income security portfolio is investment grade with a weighted-average duration of approximately 8 years for 2016 and 2015.

(2) The weighted-average credit quality rating of the other postretirement benefit assets fixed income security portfolio is investment grade with a weighted-average duration of approximately 8 years for 2016 and 7 years for 2015.

(3) The stated intents of the funds vary based on each commingled fund’s investment objective. These objectives generally include strategies to replicate or outperform various market indices. Certain standard withdrawal restrictions generally apply, which may include redemption notification period restrictions ranging from 10 to 30 days. Additionally, the fund managers retain the right to restrict withdrawals from and/or purchases into the funds so as not to disadvantage other investors in the funds. Generally, the funds also reserve the right to make all or a portion of the redemption in-kind rather than in cash or a combination of cash and in-kind.

Expected benefit payments [Table Text Block]

Following are the expected benefits to be paid by the plans. These estimates are based on the same assumptions previously discussed and reflect future service as appropriate. The actuarial assumptions are based on long-term expectations and include, but are not limited to, assumptions as to average expected retirement age and form of benefit payment. Actual benefit payments could differ significantly from expected benefit payments if near-term participant behaviors differ significantly from the actuarial assumptions.

	Pension Benefits		Other Postretirement Benefits
	(Millions)
2017	$	99	$	13
2018	103		13
2019	103		13
2020	106		13
2021	111		13
2022-2026	562		62