Cash Flow Information (Details) - USD ($) $ in Millions	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019
Supplemental Cash Flow Information [Abstract]
Cash capital expenditures and investments	$ 796	$ 924
Change in capital expenditure accruals	(1)	(17)
Total capital expenditures and investments	$ 795	$ 907

Cash outflows for purchases of and capital improvements on property, plant and equipment (capital expenditures), software, and other intangible assets as well as net cash outflows associated with the acquisition of investments.

No definition available.

Name:	mlp_CapitalExpendituresAndInvestments
Namespace Prefix:	mlp_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration