SHARE-BASED COMPENSATION - Summary of Transactions Involving Performance Awards (Details) - Long-term performance stock units shares in Thousands	9 Months Ended
	Sep. 30, 2021 $ / shares shares
Performance Units Subject to Market Conditions
Changes during the period:
Stock and stock units, beginning of period (in shares) | shares	553	[1]
Granted (in shares) | shares	576	[1]
Vested and settled (in shares) | shares	(28)	[1]
Forfeited and cancelled (in shares) | shares	(387)	[1]
Stock and stock units, end of period (in shares) | shares	714	[1]
Changes during the period:
Stock and stock units, beginning of period (in dollars per share) | $ / shares	$ 13.69
Granted (in dollars per share) | $ / shares	6.70
Vested and settled (in dollars per share) | $ / shares	25.24
Forfeited and cancelled (in dollars per share) | $ / shares	14.91
Stock and stock units, end of period (in dollars per share) | $ / shares	$ 6.45
Performance Units Not Subject to Market Conditions
Changes during the period:
Stock and stock units, beginning of period (in shares) | shares	273	[1]
Granted (in shares) | shares	110	[1]
Vested and settled (in shares) | shares	0	[1]
Forfeited and cancelled (in shares) | shares	(135)	[1]
Stock and stock units, end of period (in shares) | shares	248	[1]
Changes during the period:
Stock and stock units, beginning of period (in dollars per share) | $ / shares	$ 12.55
Granted (in dollars per share) | $ / shares	11.69
Vested and settled (in dollars per share) | $ / shares	0
Forfeited and cancelled (in dollars per share) | $ / shares	16.65
Stock and stock units, end of period (in dollars per share) | $ / shares	$ 9.94

[1] Performance units with variable payouts are shown at target level of performance.