Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Statement of Comprehensive Income [Abstract]
NET INCOME	$ 463	$ 454	$ 856	$ 837
OTHER COMPREHENSIVE LOSS:
Pension and OPEB prior service costs	(3)	(3)	(10)	(30)
Amortized losses on derivative hedges	0	0	1	1
Other comprehensive loss	(3)	(3)	(9)	(29)
Income tax benefits on other comprehensive loss	(1)	(1)	(3)	(7)
Other comprehensive loss, net of tax	(2)	(2)	(6)	(22)
COMPREHENSIVE INCOME	$ 461	$ 452	$ 850	$ 815