UNAUDITED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 146	$ 155	$ 402	$ 335
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	146	155	402	335
Less comprehensive income attributable to noncontrolling interests	5	6	14	11
Comprehensive income attributable to the Partnership	$ 141	$ 149	$ 388	$ 324