STOCKHOLDER'S EQUITY - Narrative (Details) $ / shares in Units, $ in Thousands		12 Months Ended
	Feb. 24, 2017 USD ($) shares	Dec. 31, 2019 USD ($) vote $ / shares shares	Dec. 31, 2018 USD ($) $ / shares shares	Dec. 31, 2017 USD ($)	May 25, 2018 $ / shares shares	Mar. 06, 2017 $ / shares shares
Class of Stock [Line Items]
Preferred stock, shares authorized (in shares)		100,000,000	100,000,000
Preferred stock, par value (in USD per share) | $ / shares		$ 0.0000001	$ 0.0000001
Preferred stock, shares outstanding (in shares)		0	0
Consideration paid for termination of warrants | $	$ 54,800	$ 0	$ 0	$ 54,808
Warrants to purchase shares of common, canceled (in shares)	9,500,000
Recovery of common stock in connection with indemnification settlement agreement (in shares)		20,793	469,894
Common Stock Warrant, 2022 Notes
Class of Stock [Line Items]
Outstanding warrants to purchase aggregate shares of capital stock (in shares)						19,200,000
Exercise price of warrants (in USD per share) | $ / shares						$ 31.18
Number of warrants exercised (in shares)		0
Common Stock Warrant, 2023 Notes
Class of Stock [Line Items]
Outstanding warrants to purchase aggregate shares of capital stock (in shares)					11,100,000
Exercise price of warrants (in USD per share) | $ / shares					$ 109.26
Number of warrants exercised (in shares)		0
Common Stock Warrants
Class of Stock [Line Items]
Outstanding warrants to purchase aggregate shares of capital stock (in shares)		11,100,000				19,200,000
Exercise price of warrants (in USD per share) | $ / shares		$ 109.26				$ 31.18
Shares received upon exercise of convertible notes (in shares)			7,200,000
Class A Common Stock
Class of Stock [Line Items]
Number of votes per share | vote		1
Common stock, shares authorized (in shares)		1,000,000,000	1,000,000,000
Common stock, par value (in USD per share) | $ / shares		$ 0.0000001	$ 0.0000001
Common stock, shares outstanding (in shares)		352,386,562	323,546,864
Class B Common Stock
Class of Stock [Line Items]
Number of votes per share | vote		10
Common stock, shares authorized (in shares)		500,000,000	500,000,000
Common stock, par value (in USD per share) | $ / shares		$ 0.0000001	$ 0.0000001
Common stock, shares outstanding (in shares)		80,410,158	93,501,142
2022 Notes | Common Stock Warrants
Class of Stock [Line Items]
Shares received upon exercise of convertible notes (in shares)		300,000	6,900,000
Convertible Debt | 2022 Notes
Class of Stock [Line Items]
Shares received upon exercise of convertible notes (in shares)			7,300,000