CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Comprehensive income:
Net income	$ 1,372	$ 1,261	$ 1,148
Defined pension and other postretirement benefits:
Net pension and retiree medical loss arising during the period, net of tax of $0, $(2) and $(2), respectively	0	(6)	(3)
Reclassification of loss to net income, net of tax of $1, $3 and $5, respectively	3	9	7
Derivative instruments:
Net fair value decrease, net of tax of $(8), $(2) and $0, respectively	(23)	(5)	0
Reclassification of loss to net income, net of tax of $1, $1 and $2, respectively	3	3	3
Total other comprehensive (loss) income	(17)	1	7
Total comprehensive income	$ 1,355	$ 1,262	$ 1,155