Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
-Sentence Column B

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- Definition

The aggregate fair value of assets that are already posted, at the end of the reporting period, as collateral for derivative instruments with credit-risk-related contingent features.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4H
-Subparagraph (d)
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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

The aggregate fair value amounts of derivative instruments that contain credit-risk-related contingent features that are in a net liability position at the end of the reporting period. For nonderivative instruments that are designated and qualify as hedging instruments, the fair value amounts are the carrying value of the nonderivative hedging instrument, including the adjustment for the foreign currency transaction gain (loss) on that instrument.

+ References

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-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4H
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5624258-113959

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- Definition

The cash outflow for derivative instruments during the period, which are classified as financing activities, excluding those designated as hedging instruments.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (d)
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-Publisher FASB
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-Section 45
-Paragraph 23
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Derivative Instruments - Additional Information (Detail) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Aug. 31, 2018	Dec. 31, 2018	Dec. 31, 2017
Derivative [Line Items]
Amount of collateral posted related to derivative instruments with credit-risk-related contingent features		$ 66	$ 170
Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Aggregate fair value of derivative instruments with credit-risk-related contingent features for which a net liability position existed, net of collateral		1,100	1,400
Not Designated as Hedging Instrument [Member] \| Cash Payments Related To Interest Rate Swap Agreements [Member]
Derivative [Line Items]
Total cash payments for settled interest-rate swaps		92	$ 112
Not Designated as Hedging Instrument [Member] \| Interest-Rate Swap 3 [Member]
Derivative [Line Items]
Notional principal amount of interest-rate swap	$ 200	100
Not Designated as Hedging Instrument [Member] \| Interest-Rate Swap 3 [Member] \| Cash Payments To Amend Interest Rate Swap Agreements [Member]
Derivative [Line Items]
Total cash payments for settled interest-rate swaps	$ 10
Not Designated as Hedging Instrument [Member] \| Interest Rate Swaps 1 Through 5 [Member]
Derivative [Line Items]
Notional principal amount of interest-rate swap		1,600
Western Gas Partners LP [Member] \| Not Designated as Hedging Instrument [Member] \| Interest Rate Swaps 6 Through 8 [Member]
Derivative [Line Items]
Notional principal amount of interest-rate swap		$ 750