Derivative Financial Instruments (Fair Value of Derivatives) (Detail) - USD ($) $ in Millions		Sep. 30, 2021	Dec. 31, 2020
Derivative [Line Items]
Derivative Assets		$ 47
Derivative Liability		22	$ 27
Other Current Liabilities [Member]
Derivative [Line Items]
Derivative Liability	[1]	2	2
Other Current Assets [Member]
Derivative [Line Items]
Derivative Assets	[2]	22
Other Noncurrent Liabilities [Member]
Derivative [Line Items]
Derivative Liability	[3]	20	25
Other Noncurrent Assets [Member]
Derivative [Line Items]
Derivative Assets	[4]	25
Interest Rate Contract [Member] | Other Current Liabilities [Member]
Derivative [Line Items]
Derivative Liability		2	2
Interest Rate Contract [Member] | Other Noncurrent Liabilities [Member]
Derivative [Line Items]
Derivative Liability		19	25
Commodity Contract [Member] | Other Current Assets [Member]
Derivative [Line Items]
Derivative Assets		22
Commodity Contract [Member] | Other Noncurrent Liabilities [Member]
Derivative [Line Items]
Derivative Liability		1
Commodity Contract [Member] | Other Noncurrent Assets [Member]
Derivative [Line Items]
Derivative Assets		25
Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative Assets		0
Derivative Liability		13	16
Designated as Hedging Instrument [Member] | Other Current Liabilities [Member]
Derivative [Line Items]
Derivative Liability	[1]	1	1
Designated as Hedging Instrument [Member] | Other Current Assets [Member]
Derivative [Line Items]
Derivative Assets	[2]	0
Designated as Hedging Instrument [Member] | Other Noncurrent Liabilities [Member]
Derivative [Line Items]
Derivative Liability	[3]	12	15
Designated as Hedging Instrument [Member] | Other Noncurrent Assets [Member]
Derivative [Line Items]
Derivative Assets	[4]	0
Designated as Hedging Instrument [Member] | Interest Rate Contract [Member] | Other Current Liabilities [Member]
Derivative [Line Items]
Derivative Liability		1	1
Designated as Hedging Instrument [Member] | Interest Rate Contract [Member] | Other Noncurrent Liabilities [Member]
Derivative [Line Items]
Derivative Liability		12	15
Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Other Current Assets [Member]
Derivative [Line Items]
Derivative Assets		0
Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Other Noncurrent Liabilities [Member]
Derivative [Line Items]
Derivative Liability		0
Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Other Noncurrent Assets [Member]
Derivative [Line Items]
Derivative Assets		0
Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative Assets		47
Derivative Liability		9	11
Not Designated as Hedging Instrument [Member] | Other Current Liabilities [Member]
Derivative [Line Items]
Derivative Liability	[1]	1	1
Not Designated as Hedging Instrument [Member] | Other Current Assets [Member]
Derivative [Line Items]
Derivative Assets	[2]	22
Not Designated as Hedging Instrument [Member] | Other Noncurrent Liabilities [Member]
Derivative [Line Items]
Derivative Liability	[3]	8	10
Not Designated as Hedging Instrument [Member] | Other Noncurrent Assets [Member]
Derivative [Line Items]
Derivative Assets	[4]	25
Not Designated as Hedging Instrument [Member] | Interest Rate Contract [Member] | Other Current Liabilities [Member]
Derivative [Line Items]
Derivative Liability		1	1
Not Designated as Hedging Instrument [Member] | Interest Rate Contract [Member] | Other Noncurrent Liabilities [Member]
Derivative [Line Items]
Derivative Liability		7	$ 10
Not Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Other Current Assets [Member]
Derivative [Line Items]
Derivative Assets		22
Not Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Other Noncurrent Liabilities [Member]
Derivative [Line Items]
Derivative Liability		1
Not Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Other Noncurrent Assets [Member]
Derivative [Line Items]
Derivative Assets		$ 25

[1] Current derivative liabilities are presented in other current liabilities in the Consolidated Balance Sheets.

[2] Current derivative assets are presented in other current assets in the Consolidated Balance Sheets.

[3] Noncurrent derivative liabilities are presented in other deferred credits and other liabilities in the Consolidated Balance Sheets.

[4] Noncurrent derivative assets are presented in other deferred debits and other assets in the Consolidated Balance Sheets.