Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Comprehensive Income [Abstract]
NET INCOME (LOSS)	$ 912	$ 1,348	$ (1,724)
OTHER COMPREHENSIVE INCOME (LOSS):
Pension and OPEB prior service costs	(31)	(83)	(85)
Amortized losses on derivative hedges	2	21	10
Change in unrealized gains on available-for-sale securities	0	(106)	22
Other comprehensive income (loss)	(29)	(168)	(53)
Income tax benefits on other comprehensive loss	(8)	(67)	(21)
Other comprehensive loss, net of tax	(21)	(101)	(32)
COMPREHENSIVE INCOME (LOSS)	$ 891	$ 1,247	$ (1,756)