FAIR VALUE MEASUREMENTS - FINANCIAL INSTRUMENTS (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
Mar. 31, 2018	Dec. 31, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Foreign currency translation	$ 4	$ 35
Carrying amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term amounts due from unconsolidated affiliates	627	604
Long-term amounts due to unconsolidated affiliate	35	35
Total long-term debt	22,063	17,138
Accumulated interest outstanding	35	29
Unamortized discount (net of premium) and debt issuance costs	206	143
Build-to-suit and capital lease obligations	877	877
Carrying amount [Member] \| Otay Mesa VIE [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, gross	292	295
Fair value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term amounts due from unconsolidated affiliates	647	624
Long-term amounts due to unconsolidated affiliate	32	32
Total long-term debt	22,500	18,409
Fair value [Member] \| Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term amounts due from unconsolidated affiliates	0	0
Long-term amounts due to unconsolidated affiliate	0	0
Total long-term debt	790	817
Fair value [Member] \| Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term amounts due from unconsolidated affiliates	606	528
Long-term amounts due to unconsolidated affiliate	32	32
Total long-term debt	21,254	17,134
Fair value [Member] \| Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term amounts due from unconsolidated affiliates	41	96
Long-term amounts due to unconsolidated affiliate	0	0
Total long-term debt	456	458
San Diego Gas and Electric Company [Member] \| Carrying amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total long-term debt	4,848	4,868
Unamortized discount (net of premium) and debt issuance costs	45	45
Capital lease obligations	730	732
San Diego Gas and Electric Company [Member] \| Fair value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total long-term debt	5,184	5,368
San Diego Gas and Electric Company [Member] \| Fair value [Member] \| Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total long-term debt	0	0
San Diego Gas and Electric Company [Member] \| Fair value [Member] \| Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total long-term debt	4,892	5,073
San Diego Gas and Electric Company [Member] \| Fair value [Member] \| Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total long-term debt	292	295
Southern California Gas Company [Member] \| Carrying amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total long-term debt	3,009	3,009
Unamortized discount (net of premium) and debt issuance costs	24	24
Capital lease obligations	4	1
Southern California Gas Company [Member] \| Fair value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total long-term debt	3,102	3,192
Southern California Gas Company [Member] \| Fair value [Member] \| Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total long-term debt	0	0
Southern California Gas Company [Member] \| Fair value [Member] \| Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total long-term debt	3,102	3,192
Southern California Gas Company [Member] \| Fair value [Member] \| Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total long-term debt	$ 0	$ 0

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- Definition

Capital Lease Obligations and Build-To-Suit

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Amount equal to the present value (the principal) at the beginning of the lease term of minimum lease payments during the lease term (excluding that portion of the payments representing executory costs such as insurance, maintenance, and taxes to be paid by the lessor, together with any profit thereon) net of payments or other amounts applied to the principal through the balance sheet date.

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Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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Amount before tax of foreign currency transaction realized and unrealized gain recognized in the income statement.

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Carrying amount as of the balance sheet date of interest earned but not received. Also called accrued interest or accrued interest receivable.

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Value of the investment at close of period. For investment in and advances to affiliates, if operations of any controlled companies are different in character from those of the company, group such affiliates within divisions and by type of activities.

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Fair value portion of notes payable.

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