Redeemable Preferred Units (Rollforward of Redeemable Preferred Units) (Details) - USD ($) $ in Millions		12 Months Ended
	May 13, 2016	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Redeemable Noncontrolling Interest [Line Items]
Redeemable preferred units, beginning balance		$ 1,004
Distributions to unitholders and general partner		(2,435)	$ (1,819)	$ (1,120)
Redeemable preferred units, ending balance		968	1,004
Series A Convertible Preferred Units
Redeemable Noncontrolling Interest [Line Items]
Redeemable preferred units, beginning balance		1,004	1,000
Issuance of redeemable preferred units	$ 984
Net income allocated		81	75
Distributions to unitholders and general partner		(81)	(71)
Redeemable preferred units, ending balance		968	1,004	$ 1,000
Convertible Preferred Stock Converted to Other Securities		$ (36)	$ 0