STOCK-BASED COMPENSATION (Tables)

12 Months Ended

Dec. 31, 2017

STOCK-BASED COMPENSATION

Summary of restricted stock units, performance-based stock units, and weighted average grant date fair values

	Employee Service-Based Awards				Employee Performance- Based Awards				Director Awards
	Units		Weighted Average Grant Date Fair Value		Units		Weighted Average Grant Date Fair Value		Units		Weighted Average Grant Date Fair Value
Nonvested at December 31, 2015	810,840		$	26.90	145,451		$	25.83	94,169		$	18.25
Granted	631,011		6.90		192,600		6.90		71,000		6.53
Vested	(279,421	)	26.64		(19,722	)	23.99		(93,704	)	18.16
Forfeited	(95,832	)	20.69		(192,600	)	6.90		—		—
Nonvested at December 31, 2016	1,066,598		16.30		125,729		26.11		71,465		6.72
Granted	555,280		13.74		512,458		17.21		98,406		12.66
Vested	(363,834	)	19.27		(5,551	)	29.66		(71,465	)	6.72
Forfeited	(75,005	)	14.58		—		—		—		—
Nonvested at December 31, 2017	1,183,039		$	14.30	632,636		$	18.87	98,406		$	12.66

Summary of option activity and weighted average exercise prices

	Director Awards
Weighted Average Exercise Price	Shares	Weighted Average Exercise Price		Aggregate Intrinsic Value		Weighted Average Remaining Contractual Term (Years)
Outstanding at December 31, 2016	—	$	—	$	—	—
Granted	798,020	12.77		2,378,100		9.4
Outstanding at December 31, 2017	798,020	$	12.77	$	2,378,100