Derivative Financial Instruments (Fair Value of Derivatives) (Detail) - USD ($) $ in Millions		Dec. 31, 2021	Dec. 31, 2020
Derivative [Line Items]
Derivative Assets	[1]	$ 148
Derivative Liability		19	$ 27
Other Current Assets
Derivative [Line Items]
Derivative Assets	[2]	18
Other Current Liabilities [Member]
Derivative [Line Items]
Derivative Liability	[3]	2	2
Other Noncurrent Assets
Derivative [Line Items]
Derivative Assets		130
Other Noncurrent Liabilities [Member]
Derivative [Line Items]
Derivative Liability	[4]	17	25
Commodity Contract | Other Current Assets
Derivative [Line Items]
Derivative Assets		18
Commodity Contract | Other Noncurrent Assets
Derivative [Line Items]
Derivative Assets		130
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		17	25
Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative Assets	[1]	0
Derivative Liability		12	16
Designated as Hedging Instrument [Member] | Other Current Assets
Derivative [Line Items]
Derivative Assets	[2]	0
Designated as Hedging Instrument [Member] | Other Current Liabilities [Member]
Derivative [Line Items]
Derivative Liability	[3]	1	1
Designated as Hedging Instrument [Member] | Other Noncurrent Assets
Derivative [Line Items]
Derivative Assets		0
Designated as Hedging Instrument [Member] | Other Noncurrent Liabilities [Member]
Derivative [Line Items]
Derivative Liability	[4]	11	15
Designated as Hedging Instrument [Member] | Commodity Contract | Other Current Assets
Derivative [Line Items]
Derivative Assets		0
Designated as Hedging Instrument [Member] | Commodity Contract | Other Noncurrent Assets
Derivative [Line Items]
Derivative Assets		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		11	15
Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative Assets	[1]	148
Derivative Liability		7	11
Not Designated as Hedging Instrument [Member] | Other Current Assets
Derivative [Line Items]
Derivative Assets	[2]	18
Not Designated as Hedging Instrument [Member] | Other Current Liabilities [Member]
Derivative [Line Items]
Derivative Liability	[3]	1	1
Not Designated as Hedging Instrument [Member] | Other Noncurrent Assets
Derivative [Line Items]
Derivative Assets		130
Not Designated as Hedging Instrument [Member] | Other Noncurrent Liabilities [Member]
Derivative [Line Items]
Derivative Liability	[4]	6	10
Not Designated as Hedging Instrument [Member] | Commodity Contract | Other Current Assets
Derivative [Line Items]
Derivative Assets		18
Not Designated as Hedging Instrument [Member] | Commodity Contract | Other Noncurrent Assets
Derivative [Line Items]
Derivative Assets		130
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		$ 6	$ 10

[1] Noncurrent derivative assets are presented in other deferred debits and other assets in DESC’s Consolidated Balance Sheets.

[2] Current derivative assets are presented in other current assets in DESC’s Consolidated Balance Sheets.

[3] Current derivative liabilities are presented in other current liabilities in DESC’s Consolidated Balance Sheets

[4] (4)  Noncurrent derivative liabilities are presented in other deferred credits and other liabilities in DESC’s Consolidated Balance Sheets.