SIGNIFICANT ACCOUNTING POLICIES AND OTHER FINANCIAL DATA - COLLECTION ALLOWANCES (Details) - Allowance for Doubtful Accounts [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Valuation and Qualifying Accounts Disclosure [Line Items]
Allowance balance at January 1	$ 35	$ 32	$ 34
Provisions for uncollectible accounts	16	23	20
Write-offs of uncollectible accounts	(18)	(20)	(22)
Allowance balance at December 31	33	35	32
San Diego Gas and Electric Company [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Allowance balance at January 1	8	9	7
Provisions for uncollectible accounts	8	6	7
Write-offs of uncollectible accounts	(7)	(7)	(5)
Allowance balance at December 31	9	8	9
Southern California Gas Company [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Allowance balance at January 1	21	17	17
Provisions for uncollectible accounts	4	14	11
Write-offs of uncollectible accounts	(9)	(10)	(11)
Allowance balance at December 31	$ 16	$ 21	$ 17