Equity Investments and Loans (Schedule Of Earnings From Equity Investments) (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Schedule of Equity Method Investments [Line Items]
Equity in earnings of affiliates		$ 535	$ 439	$ 223
Bakken Pipeline
Schedule of Equity Method Investments [Line Items]
Equity in earnings of affiliates	$ 226		177	69
Bayou Bridge
Schedule of Equity Method Investments [Line Items]
Equity in earnings of affiliates	31		14	12
Sand Hills
Schedule of Equity Method Investments [Line Items]
Equity in earnings of affiliates	150		119	81
Southern Hills
Schedule of Equity Method Investments [Line Items]
Equity in earnings of affiliates	43		37	27
Explorer
Schedule of Equity Method Investments [Line Items]
Equity in earnings of affiliates	33		43	21
Gray Oak Pipeline, LLC
Schedule of Equity Method Investments [Line Items]
Equity in earnings of affiliates	3		1	0
Paradigm
Schedule of Equity Method Investments [Line Items]
Equity in earnings of affiliates	14		10	(1)
Phillips 66 Partners Terminal
Schedule of Equity Method Investments [Line Items]
Equity in earnings of affiliates	25		28	8
South Texas Gateway Terminal
Schedule of Equity Method Investments [Line Items]
Equity in earnings of affiliates	0		0	0
STACK
Schedule of Equity Method Investments [Line Items]
Equity in earnings of affiliates	$ 10		$ 10	$ 6