Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Statement of Comprehensive Income [Abstract]
NET INCOME (LOSS)	$ 391	$ (458)	$ 1,023	$ 1,210
OTHER COMPREHENSIVE INCOME (LOSS):
Pension and OPEB prior service costs	(7)	(18)	(21)	(55)
Amortized losses on derivative hedges		2		19
Amortized losses on derivative hedges	0		1
Change in unrealized gains on AFS securities	0	0	0	(106)
Other comprehensive loss	(7)	(16)	(20)	(142)
Income tax benefits on other comprehensive loss	(3)	(4)	(6)	(61)
Other comprehensive loss, net of tax	(4)	(12)	(14)	(81)
COMPREHENSIVE INCOME (LOSS)	$ 387	$ (470)	$ 1,009	$ 1,129