CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Comprehensive income:
Net income	$ 295	$ 315
Pension and retiree medical benefits:
Net pension and retiree medical gains arising during the period, net of tax of $0 and $1, respectively	0	2
Reclassifications of loss to net income, net of tax of $0	1	1
Derivative instruments:
Net fair value decrease, net of tax of $(3) and $(2), respectively	(10)	(7)
Reclassification of losses to net income, net of tax of $0	2	1
Total other comprehensive loss	(7)	(3)
Total comprehensive income	$ 288	$ 312