ACCOUNTING POLICIES - Computation of Basic and Diluted Net Income (Loss) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Earnings per share
Consolidated net income	$ (42,327)	$ (47,923)	$ (64,911)	$ (50,909)	$ (95,690)	$ (786)	$ (7,499)	$ (5,903)	$ (206,070)	$ (109,878)	$ 12,522
Less: Preferred stock converted to common stock									3,098	0	0
Less: Preferred stock dividends - declared and accumulated									77	216	0
Undistributed income (loss)									(209,245)	(110,094)	12,522
Less: Undistributed loss allocated to participating securities									(4,368)	(2,960)	0
Net income (loss) attributable to common shares									$ (204,877)	$ (107,134)	$ 12,522
Net income (loss) per common share—basic:
Net income (loss) attributable to common shares-basic (in dollars per share)	$ (1.39)	$ (1.55)	$ (2.20)	$ (1.74)	$ (3.72)	$ (0.03)	$ (0.29)	$ (0.23)	$ (6.83)	$ (4.28)	$ 0.49
Weighted average common shares outstanding—basic	32,112	30,279	28,903	28,566	25,103	25,003	24,996	25,290	29,976	25,044	25,342
Effect of dilutive securities:
Stock options and restricted stock awards (in shares)									0	0	84
Weighted average common shares outstanding—diluted	32,112	30,279	28,903	28,566	25,103	25,003	24,996	25,290	29,976	25,044	25,426
Net income (loss) attributable to common shares-diluted (in dollars per share)	$ (1.39)	$ (1.55)	$ (2.20)	$ (1.74)	$ (3.72)	$ (0.03)	$ (0.29)	$ (0.23)	$ (6.83)	$ (4.28)	$ 0.49
Stock options and restricted stock awards
Anti-dilutive securities excluded from computation of earnings per share
Stock options and restricted stock units (in shares)									543	226	466
Warrant
Anti-dilutive securities excluded from computation of earnings per share
Stock options and restricted stock units (in shares)									21	78	0
Accounting Standards Update 2014-09
Anti-dilutive securities excluded from computation of earnings per share
Cumulative effect of new accounting pronouncement in period of adoption					$ 5,000					$ 5,000