STOCKHOLDERS' INVESTMENT, EARNINGS PER SHARE AND ACCUMULATED COMPREHENSIVE INCOME Earnings per Share (Details)	3 Months Ended								12 Months Ended
	Mar. 31, 2018 $ / shares	Dec. 31, 2017 $ / shares	Sep. 30, 2017 $ / shares	Jun. 30, 2017 $ / shares	Mar. 31, 2017 $ / shares	Dec. 31, 2016 $ / shares	Sep. 30, 2016 $ / shares	Jun. 30, 2016 $ / shares	Mar. 31, 2018 USD ($) $ / shares shares	Mar. 31, 2017 USD ($) $ / shares shares	Mar. 31, 2016 USD ($) $ / shares shares
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Loss available to common stockholders – basic | $									$ (195,658,000)	$ (170,536,000)	$ (73,940,000)
Interest expense on assumed conversion of 4½% Convertible Senior Notes, net of tax (1) | $									0	0	0
Loss available to common stockholders | $									$ (195,658,000)	$ (170,536,000)	$ (73,940,000)
Weighted average number of common shares outstanding – basic									35,288,579	35,044,040	34,893,844
Assumed conversion of 4½% Convertible Senior Notes outstanding during period (1)									0	0	0
Net effect of dilutive stock options, restricted stock units and restricted stock awards based on the treasury stock method									0	0	0
Weighted average number of common shares outstanding – diluted (2)									35,288,579	35,044,040	34,893,844
Basic loss per common share | $ / shares	$ (2.84)	$ (0.23)	$ (0.88)	$ (1.57)	$ (2.22)	$ (0.62)	$ (0.85)	$ (1.17)	$ (5.54)	$ (4.87)	$ (2.12)
Diluted loss per common share | $ / shares	(2.84)	$ (0.23)	$ (0.88)	$ (1.57)	$ (2.22)	$ (0.62)	$ (0.85)	$ (1.17)	$ (5.54)	$ (4.87)	$ (2.12)
Employee Stock Option [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount									2,890,140	1,815,020	1,194,783
Antidilutive Securities Excluded from Computation of Net Income, Per Outstanding Unit, Amount | $ / shares									$ 38.77	$ 31.98	$ 62.11
Restricted stock awards
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount									547,927	541,014	286,804
Antidilutive Securities Excluded from Computation of Net Income, Per Outstanding Unit, Amount | $ / shares									$ 21.00	$ 26.76	$ 37.27
Convertible debt | 4½% Convertible Senior Notes
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Debt Instrument, Convertible, Conversion Price | $ / shares	$ 15.64								$ 15.64
Debt Instrument, Convertible, Conversion Ratio									63.9488
Debt Instrument, Convertible, Conversion Per Principal Amount | $									$ 1,000