CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 556	$ 546	$ 482
Other comprehensive loss, net of tax:
Remeasurements of pension and other postretirement benefits related to equity method investments, net of tax	(1)	(2)	0
Comprehensive income	555	544	482
Noncontrolling interests	13	18	18
Comprehensive income attributable to the Partnership	$ 542	$ 526	$ 464