Derivative Financial Instruments (Fair Value of Derivatives) (Detail) - USD ($) $ in Millions		Mar. 31, 2022	Dec. 31, 2021
Derivative [Line Items]
Derivative Assets		$ 225	$ 148
Derivative Liability		10	19
Other Current Assets [Member]
Derivative [Line Items]
Derivative Assets	[1]	52	18
Other Current Liabilities [Member]
Derivative [Line Items]
Derivative Liability	[2]	1	2
Other Noncurrent Assets [Member]
Derivative [Line Items]
Derivative Assets	[3]	173	130
Other Noncurrent Liabilities [Member]
Derivative [Line Items]
Derivative Liability	[4]	9	17
Interest Rate Contract [Member] | Other Current Liabilities [Member]
Derivative [Line Items]
Derivative Liability		1	2
Interest Rate Contract [Member] | Other Noncurrent Liabilities [Member]
Derivative [Line Items]
Derivative Liability		9	17
Commodity Contract [Member] | Other Current Assets [Member]
Derivative [Line Items]
Derivative Assets		52	18
Commodity Contract [Member] | Other Noncurrent Assets [Member]
Derivative [Line Items]
Derivative Assets		173	130
Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative Assets		0	0
Derivative Liability		7	12
Designated as Hedging Instrument [Member] | Other Current Assets [Member]
Derivative [Line Items]
Derivative Assets	[1]	0	0
Designated as Hedging Instrument [Member] | Other Current Liabilities [Member]
Derivative [Line Items]
Derivative Liability	[2]	1	1
Designated as Hedging Instrument [Member] | Other Noncurrent Assets [Member]
Derivative [Line Items]
Derivative Assets	[3]	0	0
Designated as Hedging Instrument [Member] | Other Noncurrent Liabilities [Member]
Derivative [Line Items]
Derivative Liability	[4]	6	11
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		6	11
Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Other Current Assets [Member]
Derivative [Line Items]
Derivative Assets		0	0
Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Other Noncurrent Assets [Member]
Derivative [Line Items]
Derivative Assets		0	0
Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative Assets		225	148
Derivative Liability		3	7
Not Designated as Hedging Instrument [Member] | Other Current Assets [Member]
Derivative [Line Items]
Derivative Assets	[1]	52	18
Not Designated as Hedging Instrument [Member] | Other Current Liabilities [Member]
Derivative [Line Items]
Derivative Liability	[2]	0	1
Not Designated as Hedging Instrument [Member] | Other Noncurrent Assets [Member]
Derivative [Line Items]
Derivative Assets	[3]	173	130
Not Designated as Hedging Instrument [Member] | Other Noncurrent Liabilities [Member]
Derivative [Line Items]
Derivative Liability	[4]	3	6
Not Designated as Hedging Instrument [Member] | Interest Rate Contract [Member] | Other Current Liabilities [Member]
Derivative [Line Items]
Derivative Liability		0	1
Not Designated as Hedging Instrument [Member] | Interest Rate Contract [Member] | Other Noncurrent Liabilities [Member]
Derivative [Line Items]
Derivative Liability		3	6
Not Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Other Current Assets [Member]
Derivative [Line Items]
Derivative Assets		52	18
Not Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Other Noncurrent Assets [Member]
Derivative [Line Items]
Derivative Assets		$ 173	$ 130

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

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

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

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