Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
NET INCOME (LOSS)	$ 1,348	$ (1,724)	$ (6,177)
OTHER COMPREHENSIVE INCOME (LOSS):
Pension and OPEB prior service costs	(83)	(85)	(59)
Amortized losses on derivative hedges	21	10	8
Change in unrealized gains on available-for-sale securities	(106)	22	55
Other comprehensive income (loss)	(168)	(53)	4
Income taxes (benefits) on other comprehensive income (loss)	(67)	(21)	1
Other comprehensive income (loss), net of tax	(101)	(32)	3
COMPREHENSIVE INCOME (LOSS)	$ 1,247	$ (1,756)	$ (6,174)