UNAUDITED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Statement of Comprehensive Income [Abstract]
Net income	$ 144	$ 119	$ 286	$ 256
Other comprehensive loss, net of tax:
Remeasurements of pension and other postretirement benefits related to equity method investments, net of tax	0	0	0	0
Comprehensive income	144	119	286	256
Less comprehensive income attributable to noncontrolling interests	3	4	7	9
Comprehensive income attributable to the Partnership	$ 141	$ 115	$ 279	$ 247