Equity Investments - Equity Investments Table (Details) - USD ($) $ in Thousands		3 Months Ended			6 Months Ended
		Jun. 30, 2019	Jun. 30, 2018	[1]	Jun. 30, 2019	Jun. 30, 2018	[1]
Schedule of Equity Method Investments [Line Items]
Balance	[1]				$ 1,092,088
Acquisitions					92,546
Equity income, net		$ 63,598	$ 49,430		121,590	$ 79,659
Contributions					77,333	27,490
Distributions					(115,483)	(65,525)
Distributions in excess of cumulative earnings					(17,052)	$ (13,632)
Balance		1,249,509			1,249,509
Equity Investments [Member]
Schedule of Equity Method Investments [Line Items]
Distributions					(116,996)
Fort Union [Member]
Schedule of Equity Method Investments [Line Items]
Balance					2,259
Acquisitions					0
Equity income, net					(1,093)
Contributions					0
Distributions					0
Distributions in excess of cumulative earnings					(389)
Balance		777			777
White Cliffs [Member]
Schedule of Equity Method Investments [Line Items]
Balance					43,020
Acquisitions					0
Equity income, net					5,689
Contributions					3,925
Distributions					(5,398)
Distributions in excess of cumulative earnings					(1,756)
Balance		45,480			45,480
Rendezvous [Member]
Schedule of Equity Method Investments [Line Items]
Balance					37,841
Acquisitions					0
Equity income, net					341
Contributions					0
Distributions					(1,312)
Distributions in excess of cumulative earnings					(1,614)
Balance		35,256			35,256
Mont Belvieu JV [Member]
Schedule of Equity Method Investments [Line Items]
Balance					104,949
Acquisitions					0
Equity income, net					14,404
Contributions					0
Distributions					(14,424)
Distributions in excess of cumulative earnings					(1,376)
Balance		103,553			103,553
Texas Express Gathering [Member]
Schedule of Equity Method Investments [Line Items]
Balance					19,358
Acquisitions					0
Equity income, net					1,847
Contributions					0
Distributions					(1,858)
Distributions in excess of cumulative earnings					(493)
Balance		18,854			18,854
Texas Express Pipeline [Member]
Schedule of Equity Method Investments [Line Items]
Balance					193,198
Acquisitions					0
Equity income, net					16,322
Contributions					11,020
Distributions					(16,785)
Distributions in excess of cumulative earnings					0
Balance		203,755			203,755
Front Range Pipeline [Member]
Schedule of Equity Method Investments [Line Items]
Balance					176,436
Acquisitions					0
Equity income, net					16,251
Contributions					10,175
Distributions					(15,483)
Distributions in excess of cumulative earnings					0
Balance		187,379			187,379
Whitethorn LLC [Member]
Schedule of Equity Method Investments [Line Items]
Balance					161,858
Acquisitions					0
Equity income, net					44,921
Contributions					8,865
Distributions					(40,359)
Distributions in excess of cumulative earnings					(6,359)
Balance		168,926			168,926
Cactus II [Member]
Schedule of Equity Method Investments [Line Items]
Balance					106,360
Acquisitions					0
Equity income, net					0
Contributions					34,643
Distributions					0
Distributions in excess of cumulative earnings					0
Balance		141,003			141,003
Capitalized interest					3,100
Saddlehorn [Member]
Schedule of Equity Method Investments [Line Items]
Balance					108,507
Acquisitions					0
Equity income, net					11,438
Contributions					1,026
Distributions					(8,180)
Distributions in excess of cumulative earnings					0
Balance		112,791			112,791
Panola [Member]
Schedule of Equity Method Investments [Line Items]
Balance					22,769
Acquisitions					0
Equity income, net					1,075
Contributions					0
Distributions					(1,075)
Distributions in excess of cumulative earnings					(553)
Balance		22,216			22,216
Mi Vida [Member]
Schedule of Equity Method Investments [Line Items]
Balance					64,631
Acquisitions					0
Equity income, net					5,840
Contributions					0
Distributions					(6,193)
Distributions in excess of cumulative earnings					(2,743)
Balance		61,535			61,535
Ranch Westex [Member]
Schedule of Equity Method Investments [Line Items]
Balance					50,902
Acquisitions					0
Equity income, net					3,745
Contributions					0
Distributions					(5,119)
Distributions in excess of cumulative earnings					(1,465)
Balance		48,063			48,063
Red Bluff Express [Member]
Schedule of Equity Method Investments [Line Items]
Balance					0
Acquisitions					92,546
Equity income, net					810
Contributions					7,679
Distributions					(810)
Distributions in excess of cumulative earnings					(304)
Balance		$ 99,921			$ 99,921

[1] Financial information has been recast to include the financial position and results attributable to AMA. See Note 1 and Note 3.