FAIR VALUE MEASUREMENTS - FINANCIAL INSTRUMENTS (Details) - USD ($) $ in Millions		3 Months Ended	12 Months Ended
		Mar. 31, 2016	Dec. 31, 2015
Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of financial instruments, Total long-term debt	[1],[2]	$ 13,761	$ 13,761
Preferred Stock Of Subsidiaries Fair Value Disclosure		20	20
Due from affiliate, noncurrent, Fair Value Disclosure	[3]	173	175
Debt Instrument Increase Accrued Interest		13	11
Unamortized Discount and Debt Issuance Costs		106	107
Build-To-Suit and Capital Lease Obligations		386	387
Carrying Amount | Otay Mesa Energy Center Loan Payable Currently Through April 2019 Member [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument Carrying Amount		312	315
Carrying Amount | San Diego Gas and Electric Company [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of financial instruments, Total long-term debt	[2],[4]	4,285	4,304
Capital Lease Obligations		243	244
Unamortized Discount and Debt Issuance Costs		43	43
Carrying Amount | Southern California Gas Company [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of financial instruments, Total long-term debt	[5]	2,513	2,513
Preferred Stock Of Subsidiaries Fair Value Disclosure		22	22
Capital Lease Obligations		1	1
Unamortized Discount and Debt Issuance Costs		24	24
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of financial instruments, Total long-term debt	[1],[2]	15,015	14,633
Preferred Stock Of Subsidiaries Fair Value Disclosure		23	23
Due from affiliate, noncurrent, Fair Value Disclosure	[3]	164	166
Fair Value | Fair Value, Inputs, Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of financial instruments, Total long-term debt	[1],[2]	0	0
Preferred Stock Of Subsidiaries Fair Value Disclosure		0	0
Due from affiliate, noncurrent, Fair Value Disclosure	[3]	0	0
Fair Value | Fair Value, Inputs, Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of financial instruments, Total long-term debt	[1],[2]	14,363	13,985
Preferred Stock Of Subsidiaries Fair Value Disclosure		23	23
Due from affiliate, noncurrent, Fair Value Disclosure	[3]	92	97
Fair Value | Fair Value, Inputs, Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of financial instruments, Total long-term debt	[1],[2]	652	648
Preferred Stock Of Subsidiaries Fair Value Disclosure		0	0
Due from affiliate, noncurrent, Fair Value Disclosure	[3]	72	69
Fair Value | San Diego Gas and Electric Company [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of financial instruments, Total long-term debt	[2],[4]	4,829	4,670
Fair Value | San Diego Gas and Electric Company [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of financial instruments, Total long-term debt	[2],[4]	0	0
Fair Value | San Diego Gas and Electric Company [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of financial instruments, Total long-term debt	[2],[4]	4,517	4,355
Fair Value | San Diego Gas and Electric Company [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of financial instruments, Total long-term debt	[2],[4]	312	315
Fair Value | Southern California Gas Company [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of financial instruments, Total long-term debt	[5]	2,731	2,621
Preferred Stock Of Subsidiaries Fair Value Disclosure		25	25
Fair Value | Southern California Gas Company [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of financial instruments, Total long-term debt	[5]	0	0
Preferred Stock Of Subsidiaries Fair Value Disclosure		0	0
Fair Value | Southern California Gas Company [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of financial instruments, Total long-term debt	[5]	2,731	2,621
Preferred Stock Of Subsidiaries Fair Value Disclosure		25	25
Fair Value | Southern California Gas Company [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of financial instruments, Total long-term debt	[5]	0	0
Preferred Stock Of Subsidiaries Fair Value Disclosure		$ 0	$ 0

[1] Before reductions for unamortized discount (net of premium) and debt issuance costs of $106 million and $107 million at March 31, 2016 and December 31, 2015, respectively, and excluding build-to-suit and capital lease obligations of $386 million and $387 million at March 31, 2016 and December 31, 2015, respectively. We discuss our long-term debt in Note 6 above and in Note 5 of the Notes to Consolidated Financial Statements in the Annual Report.

[2] Level 3 instruments include $312 million and $315 million at March 31, 2016 and December 31, 2015, respectively, related to Otay Mesa VIE.

[3] Excluding accumulated interest outstanding of $13 million and $11 million at March 31, 2016 and December 31, 2015, respectively.

[4] Before reductions for unamortized discount and debt issuance costs of $43 million at March 31, 2016 and December 31, 2015, and excluding capital lease obligations of $243 million and $244 million at March 31, 2016 and December 31, 2015, respectively.

[5] Before reductions for unamortized discount and debt issuance costs of $24 million at March 31, 2016 and December 31, 2015, and excluding capital lease obligations of $1 million at March 31, 2016 and December 31, 2015.