OTHER FINANCIAL DATA - SHAREHOLDER'S EQUITY AND NONCONTROLLING INTEREST (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2017		Mar. 31, 2016	Dec. 31, 2015
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Equity, beginning of period		$ 15,241	[1]	$ 12,579
Equity, beginning of period	[1]	12,951
Cumulative-effect adjustment from change in accounting principle					$ 107
Comprehensive income (loss)		515		349
Share-based compensation expense		10		13
Common stock dividends declared		(206)		(188)
Issuances of common stock		30		28
Repurchases of common stock		(14)		(54)
Distributions to noncontrolling interests		(7)		(3)
Equity, end of period		15,569		12,831
Equity, end of period		13,264
Parent [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Equity, beginning of period		12,951		11,809
Cumulative-effect adjustment from change in accounting principle					107
Comprehensive income (loss)		493		338
Share-based compensation expense		10		13
Common stock dividends declared		(206)		(188)
Issuances of common stock		30		28
Repurchases of common stock		(14)		(54)
Distributions to noncontrolling interests		0		0
Equity, end of period		13,264		12,053
Noncontrolling Interest [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Equity, beginning of period		2,290		770
Cumulative-effect adjustment from change in accounting principle					0
Comprehensive income (loss)		22		11
Share-based compensation expense		0		0
Common stock dividends declared		0		0
Issuances of common stock		0		0
Repurchases of common stock		0		0
Distributions to noncontrolling interests		(7)		(3)
Equity, end of period		2,305		778
San Diego Gas and Electric Company [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Equity, beginning of period		5,678	[1]	5,276
Equity, beginning of period	[1]	5,641
Cumulative-effect adjustment from change in accounting principle					23
Comprehensive income (loss)		160		135
Common stock dividends declared		(175)
Distributions to noncontrolling interests		(3)		(1)
Equity, end of period		5,660		5,433
Equity, end of period		5,621
San Diego Gas and Electric Company [Member] | Parent [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Equity, beginning of period		5,641		5,223
Cumulative-effect adjustment from change in accounting principle					23
Comprehensive income (loss)		155		136
Common stock dividends declared		(175)
Distributions to noncontrolling interests		0		0
Equity, end of period		5,621		5,382
San Diego Gas and Electric Company [Member] | Noncontrolling Interest [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Equity, beginning of period		37		53
Cumulative-effect adjustment from change in accounting principle					0
Comprehensive income (loss)		5		(1)
Common stock dividends declared		0
Distributions to noncontrolling interests		(3)		(1)
Equity, end of period		39		51
Southern California Gas Company [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Equity, beginning of period		3,510	[1]	3,149
Cumulative-effect adjustment from change in accounting principle					$ 15
Comprehensive income (loss)		203		199
Equity, end of period		$ 3,713		$ 3,363

[1] Derived from audited financial statements.