Note 6 - Equity Method Investments and Joint Ventures Equity Method Investments, Table (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2018		Dec. 31, 2017		Dec. 31, 2016
Schedule of Equity Method Investments [Line Items]
Payments to Acquire Equity Method Investments		$ 186		$ 120
Equity Method Investments		440	[1]	337
Equity in earnings	[2]	31		22		$ 13
Cumulative Effect of New Accounting Principle in Period of Adoption		(3)
Distributions received		(52)		(39)
Equity Method Investments		602		440	[1]	337
Rangeland RIO Pipeline, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Payments to Acquire Equity Method Investments	[3]	159		0
Equity Method Investments	[3]	0	[4]	0
Equity in earnings	[3]	6		0
Cumulative Effect of New Accounting Principle in Period of Adoption	[3]	0
Distributions received	[3]	(5)		0
Equity Method Investments		160	[4]	0	[3],[4]	0	[3]
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity		75		0	[5]
Minnesota Pipe Line Company, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Payments to Acquire Equity Method Investments	[3]	0		120
Equity Method Investments	[3]	120	[4]	0
Equity in earnings	[3]	17		12
Cumulative Effect of New Accounting Principle in Period of Adoption	[3]	0
Distributions received	[3]	(20)		(12)
Equity Method Investments		117	[4]	120	[3],[4]	0	[3]
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity		34		35	[5]
PNAC [Member]
Schedule of Equity Method Investments [Line Items]
Payments to Acquire Equity Method Investments	[3]	27		0
Equity Method Investments	[3]	0	[4]	0
Equity in earnings	[3]	(1)		0
Cumulative Effect of New Accounting Principle in Period of Adoption	[3]	0
Distributions received	[3]	0		0
Equity Method Investments		26	[4]	0	[3],[4]	0	[3]
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity		17		0	[5]
Rendezvous Gas Services, L.L.C.
Schedule of Equity Method Investments [Line Items]
Payments to Acquire Equity Method Investments		0		0	[3]
Equity Method Investments		268	[4]	281
Equity in earnings		5		6
Cumulative Effect of New Accounting Principle in Period of Adoption		0
Distributions received		(20)		(19)
Equity Method Investments		253	[4]	268	[4]	281
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity		125		130
Three Rivers Gathering, LLC
Schedule of Equity Method Investments [Line Items]
Payments to Acquire Equity Method Investments		0		0	[3]
Equity Method Investments		37	[4]	40
Equity in earnings		3		2
Cumulative Effect of New Accounting Principle in Period of Adoption		(3)
Distributions received		(5)		(5)
Equity Method Investments		32	[4]	37	[4]	40
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity		14		15
Uintah Basin Field Services, LLC
Schedule of Equity Method Investments [Line Items]
Payments to Acquire Equity Method Investments		0		0	[3]
Equity Method Investments		15	[4]	16
Equity in earnings		1		2
Cumulative Effect of New Accounting Principle in Period of Adoption		0
Distributions received		(2)		(3)
Equity Method Investments		14	[4]	15	[4]	$ 16
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity		$ 6		$ 6

[1] Adjusted to include the historical results of the Predecessors. See Notes 1 and 2 for further discussion.

[2] All periods include the historical results of the Predecessors. See Notes 1 and 2 for further discussion.

[3] These equity method investments were included in the 2018 Drop Down. Amounts were adjusted to include the historical results of the Predecessors. See Notes 1 and 2 for further discussion.

[4] The carrying amounts of our investments that exceed the underlying equity in net assets are amortized over the useful life of the underlying fixed assets and included in equity in earnings. The carrying amount of our investments in these equity method investments exceeded the underlying equity in net assets as shown below. December 31,(in millions)2018 2017 (c)ALRP$75 $—MPL34 35PNAC17 —RGS125 130TRG14 15UBFS6 6

[5] Adjusted to include the historical results of the Predecessors. See Notes 1 and 2 for further discussion.