EQUITY METHOD INTERESTS - Information of Equity Method Investments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Dec. 31, 2019
Schedule of Equity Method Investments [Line Items]
Equity method interests	$ 1,408,479		$ 1,408,479		$ 1,408,479	$ 1,258,048
Difference between carrying amount and underlying equity					34,700	29,700
Movement In Equity Method Interests [Roll Forward]
Balance at December 31, 2019			1,258,048
Contributions			154,386	$ 210,238
Distributions			(41,747)
Capitalized interest			5,365
Equity income (loss), net	16,923	$ (1,297)	33,221	$ (1,028)
Accumulated other comprehensive loss			(794)
Balance at June 30, 2020	1,408,479		1,408,479
Retained earnings, undistributed earnings					$ 3,000
Gulf Coast Express Pipeline LLC
Schedule of Equity Method Investments [Line Items]
Ownership percentage					16.00%
Equity method interests	286,833		291,628		$ 286,833	291,628
Movement In Equity Method Interests [Roll Forward]
Balance at December 31, 2019			291,628
Contributions			919
Distributions			(26,171)
Capitalized interest			0
Equity income (loss), net			20,457
Accumulated other comprehensive loss			0
Balance at June 30, 2020	286,833		286,833
EPIC Crude Holdings, LP
Schedule of Equity Method Investments [Line Items]
Ownership percentage					15.00%
Equity method interests	175,051		175,051		$ 175,051	163,199
Movement In Equity Method Interests [Roll Forward]
Balance at December 31, 2019			163,199
Contributions			15,000
Distributions			0
Capitalized interest			0
Equity income (loss), net			(2,354)
Accumulated other comprehensive loss			(794)
Balance at June 30, 2020	175,051		175,051
Permian Highway Pipeline LLC
Schedule of Equity Method Investments [Line Items]
Ownership percentage					26.70%
Equity method interests	454,381		310,421		$ 454,381	310,421
Movement In Equity Method Interests [Roll Forward]
Balance at December 31, 2019			310,421
Contributions			138,467
Distributions			0
Capitalized interest			5,365
Equity income (loss), net			128
Accumulated other comprehensive loss			0
Balance at June 30, 2020	454,381		454,381
Breviloba, LLC
Schedule of Equity Method Investments [Line Items]
Ownership percentage					33.00%
Equity method interests	492,214		492,800		$ 492,214	$ 492,800
Movement In Equity Method Interests [Roll Forward]
Balance at December 31, 2019			492,800
Contributions			0
Distributions			(15,576)
Capitalized interest			0
Equity income (loss), net			14,990
Accumulated other comprehensive loss			0
Balance at June 30, 2020	$ 492,214		$ 492,214