UNAUDITED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Statement of Comprehensive Income [Abstract]
Net income	$ 137	$ 146	$ 423	$ 402
Other comprehensive income, net of tax:
Remeasurements of pension and other postretirement benefits related to equity method investments, net of tax	2	0	2	0
Comprehensive income	139	146	425	402
Less comprehensive income attributable to noncontrolling interests	2	5	9	14
Comprehensive income attributable to the Partnership	$ 137	$ 141	$ 416	$ 388