EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Numerator:
Income (loss) from continuing operations	$ (21,711)	$ (23,125)	$ (48,473)	$ (34,554)	$ (72,869)	$ (21,193)	$ 25,174	$ 15,898	$ (127,863)	$ (52,990)	$ 420,474
Loss from discontinued operations									(349)	(3,838)	(47)
NET INCOME (LOSS)	$ (22,532)	$ (21,799)	$ (48,818)	$ (35,063)	$ (72,835)	$ (21,200)	$ 21,205	$ 16,002	(128,212)	(56,828)	420,427
Adjustment for basic earnings per share:
Earnings allocated to unvested shareholders									(1,811)	(1,858)	(2,163)
Numerator for basic earnings per share:
From continuing operations									(129,674)	(54,848)	418,311
From discontinued operations									(349)	(3,838)	(47)
Net income (loss) attributable to parent, basic									(130,023)	(58,686)	418,264
Adjustment for diluted earnings per share:
Effect of reallocating undistributed earnings of unvested shareholders											6
Numerator for diluted earnings per share:
From continuing operations									(129,674)	(54,848)	418,317
From discontinued operations									(349)	(3,838)	(47)
Net income (loss) attributable to parent, diluted									$ (130,023)	$ (58,686)	$ 418,270
Denominator:
Denominator for basic earnings per share – weighted-average shares									108,500	107,996	107,754
Effect of dilutive shares from stock options and restricted stock (in shares)											816
Denominator for diluted earnings per share – adjusted weighted-average shares									108,500	107,996	108,570
Basic earnings per common share:
Income (loss) from continuing operations (in dollars per share)	$ (0.20)	$ (0.22)	$ (0.45)	$ (0.33)	$ (0.68)	$ (0.20)	$ 0.23	$ 0.15	$ (1.20)	$ (0.50)	$ 3.88
Loss from discontinued operations (in dollars per share)										(0.04)
Net income (loss) (in dollars per share)	(0.21)	(0.21)	(0.45)	(0.33)	(0.68)	(0.20)	0.19	0.15	(1.20)	(0.54)	3.88
Diluted earnings per common share:
Income (loss) from continuing operations (in dollars per share)	(0.20)	(0.22)	(0.45)	(0.33)	(0.68)	(0.20)	0.23	0.15	(1.20)	(0.50)	3.85
Loss from discontinued operations (in dollars per share)										(0.04)
Net income (loss) (in dollars per share)	$ (0.21)	$ (0.21)	$ (0.45)	$ (0.33)	$ (0.68)	$ (0.20)	$ 0.19	$ 0.15	$ (1.20)	$ (0.54)	$ 3.85
Outstanding equity awards
Shares excluded from calculation of diluted earnings per share (in shares)									1,008	1,788	667
Weighted-average price per share (in dollars per share)									$ 74.38	$ 63.73	$ 72.85