GENERAL INFORMATION AND OTHER FINANCIAL DATA - INCOME TAXES (Details) - USD ($) $ in Millions	3 Months Ended				12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017		Dec. 31, 2017
Income Tax Expense And Effective Income Tax Rates Disclosure [Line Items]
Federal tax rate	21.00%				35.00%
Pretax income	$ 672		$ 755
Income tax expense	$ 289		$ 295	[1]
ETR	43.00%		39.00%
Equity earnings, before income tax	$ 5		$ 3
TCJA provisional income tax expense	25	$ 870
Income tax expense from transactional effects of foreign currency and inflation	94		97
Income tax expense from transactional effects of foreign currency and inflation net of noncontrolling interest	63		65
Gain (loss) from foreign currency derivatives	44		65
Gain (loss) from foreign currency derivatives after-tax	32		39
San Diego Gas and Electric Company [Member]
Income Tax Expense And Effective Income Tax Rates Disclosure [Line Items]
Pretax income	225		247
Income tax expense	$ 56		$ 90	[1]
ETR	25.00%		36.00%
TCJA provisional income tax expense	$ (38)
Southern California Gas Company [Member]
Income Tax Expense And Effective Income Tax Rates Disclosure [Line Items]
Pretax income	284		$ 301
Income tax expense	$ 59		$ 98	[1]
ETR	21.00%		33.00%
TCJA provisional income tax expense	$ 5

[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.