GENERAL INFORMATION AND OTHER FINANCIAL DATA - INCOME TAXES (Details) - USD ($)	3 Months Ended				9 Months Ended			12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017		Sep. 30, 2018	Sep. 30, 2017		Dec. 31, 2017
Income Tax Expense And Effective Income Tax Rates Disclosure [Line Items]
Income Tax Expense (Benefit)	$ 167,000,000		$ (84,000,000)	[1]	$ (127,000,000)	$ 378,000,000	[1]
Income (loss) before income taxes and equity earnings of unconsolidated subsidiaries	427,000,000		5,000,000	[1]	(15,000,000)	1,154,000,000	[1]
Equity (losses) earnings, before income tax	(52,000,000)		10,000,000		(236,000,000)	31,000,000
Pretax income (loss)	$ 375,000,000		$ 15,000,000		$ (251,000,000)	$ 1,185,000,000
Effective income tax rate	45.00%		(560.00%)		51.00%	32.00%
Federal tax rate					21.00%			35.00%
TCJA provisional income tax expense	$ 25,000,000	$ 870,000,000
San Diego Gas and Electric Company [Member]
Income Tax Expense And Effective Income Tax Rates Disclosure [Line Items]
Income Tax Expense (Benefit)	53,000,000		$ (72,000,000)	[1]	$ 151,000,000	$ 72,000,000	[1]
Income (loss) before income taxes and equity earnings of unconsolidated subsidiaries	269,000,000		(91,000,000)	[1]	682,000,000	363,000,000	[1]
Pretax income (loss)	$ 269,000,000		$ (91,000,000)		$ 682,000,000	$ 363,000,000
Effective income tax rate	20.00%		79.00%		22.00%	20.00%
TCJA increase (decrease) in deferred tax liabilities					$ (38,000,000)
Southern California Gas Company [Member]
Income Tax Expense And Effective Income Tax Rates Disclosure [Line Items]
Income Tax Expense (Benefit)	$ (7,000,000)		$ (14,000,000)	[1]	75,000,000	$ 103,000,000	[1]
Income (loss) before income taxes and equity earnings of unconsolidated subsidiaries	(21,000,000)		(7,000,000)	[1]	320,000,000	372,000,000	[1]
Pretax income (loss)	$ (21,000,000)		$ (7,000,000)		$ 320,000,000	$ 372,000,000
Effective income tax rate	33.00%		200.00%		23.00%	28.00%
TCJA increase (decrease) in deferred tax liabilities					$ 5,000,000

[1] As adjusted for the retrospective adoption of ASU 2017-07, which we discuss in Note 2, and a reclassification to conform to current year presentation, which we discuss in Note 1.