Equity Investments - Equity Investments Table (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Schedule of Equity Method Investments [Line Items]
Balance	$ 1,285,717
Equity income, net	61,347	$ 57,992
Contributions	10,960	36,543
Distributions	(60,868)	(54,221)
Distributions in excess of cumulative earnings	(5,052)	$ (7,792)
Balance	1,292,104
Fort Union [Member]
Schedule of Equity Method Investments [Line Items]
Balance	(610)
Equity income, net	155
Contributions	0
Distributions	0
Distributions in excess of cumulative earnings	0
Balance	(455)
White Cliffs [Member]
Schedule of Equity Method Investments [Line Items]
Balance	45,877
Equity income, net	2,373
Contributions	0
Distributions	(2,227)
Distributions in excess of cumulative earnings	(382)
Balance	45,641
Rendezvous [Member]
Schedule of Equity Method Investments [Line Items]
Balance	32,964
Equity income, net	78
Contributions	0
Distributions	(564)
Distributions in excess of cumulative earnings	(789)
Balance	31,689
Mont Belvieu JV [Member]
Schedule of Equity Method Investments [Line Items]
Balance	103,036
Equity income, net	7,046
Contributions	0
Distributions	(7,056)
Distributions in excess of cumulative earnings	(919)
Balance	102,107
Texas Express Gathering [Member]
Schedule of Equity Method Investments [Line Items]
Balance	18,199
Equity income, net	1,062
Contributions	0
Distributions	(1,068)
Distributions in excess of cumulative earnings	(1,147)
Balance	17,046
Texas Express Pipeline [Member]
Schedule of Equity Method Investments [Line Items]
Balance	203,556
Equity income, net	8,710
Contributions	0
Distributions	(10,120)
Distributions in excess of cumulative earnings	0
Balance	202,146
Front Range Pipeline [Member]
Schedule of Equity Method Investments [Line Items]
Balance	207,782
Equity income, net	9,798
Contributions	3,670
Distributions	(11,185)
Distributions in excess of cumulative earnings	(648)
Balance	209,417
Whitethorn LLC [Member]
Schedule of Equity Method Investments [Line Items]
Balance	161,665
Equity income, net	10,242
Contributions	278
Distributions	(8,558)
Distributions in excess of cumulative earnings	0
Balance	163,627
Cactus II [Member]
Schedule of Equity Method Investments [Line Items]
Balance	172,165
Equity income, net	8,008
Contributions	6,360
Distributions	(7,608)
Distributions in excess of cumulative earnings	0
Balance	178,925
Saddlehorn [Member]
Schedule of Equity Method Investments [Line Items]
Balance	112,855
Equity income, net	6,738
Contributions	0
Distributions	(7,254)
Distributions in excess of cumulative earnings	0
Balance	112,339
Panola [Member]
Schedule of Equity Method Investments [Line Items]
Balance	21,783
Equity income, net	438
Contributions	0
Distributions	(438)
Distributions in excess of cumulative earnings	(287)
Balance	21,496
Mi Vida [Member]
Schedule of Equity Method Investments [Line Items]
Balance	57,807
Equity income, net	2,308
Contributions	0
Distributions	(1,396)
Distributions in excess of cumulative earnings	0
Balance	58,719
Ranch Westex [Member]
Schedule of Equity Method Investments [Line Items]
Balance	46,678
Equity income, net	3,189
Contributions	0
Distributions	(2,192)
Distributions in excess of cumulative earnings	(705)
Balance	46,970
Red Bluff Express [Member]
Schedule of Equity Method Investments [Line Items]
Balance	101,960
Equity income, net	1,202
Contributions	652
Distributions	(1,202)
Distributions in excess of cumulative earnings	(175)
Balance	$ 102,437