EQUITY - Common Stock and Warrants (Details) - $ / shares	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018	Nov. 09, 2018	Nov. 08, 2018	Aug. 07, 2018	Dec. 31, 2017
Class of Stock [Line Items]
Number of warrant outstanding	12,577,350
Warrant expiration period	5 years
Warrant redemption price	$ 0.01
Period of notice prior to warrant redemption	30 days
Warrant redemption stock price trigger	$ 18.00
Warrant redemption threshold trading period	20 days
Warrant redemption threshold consecutive trading period	30 days
Class A Common Stock
Class of Stock [Line Items]
Common stock, shares authorized (in shares	1,500,000,000	1,500,000,000
Common stock, par value (in USD per share)	$ 0.0001	$ 0.0001
Common stock, shares outstanding (in shares)	74,929,305	74,929,305	74,929,305	67,616,277	65,496,277	37,732,112
Warrant exercise price (in USD per share)	$ 11.50
Class C Common Stock
Class of Stock [Line Items]
Common stock, shares authorized (in shares	1,500,000,000	1,500,000,000
Common stock, par value (in USD per share)	$ 0.0001	$ 0.0001
Common stock, shares outstanding (in shares)	250,000,000	250,000,000	250,000,000	0	0	0
Private Placement
Class of Stock [Line Items]
Number of warrant outstanding	6,364,281
Apache
Class of Stock [Line Items]
Number of warrant outstanding	3,182,140