EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Numerator:
Income (loss) from continuing operations	$ (72,869)	$ (21,193)	$ 25,174	$ 15,898	$ (27,590)	$ 90,899	$ 153,542	$ 203,623	$ (52,990)	$ 420,474	$ 706,610
Loss from discontinued operations									(3,838)	(47)	(47)
NET INCOME (LOSS)	$ (72,835)	$ (21,200)	$ 21,205	$ 16,002	$ (27,596)	$ 90,872	$ 153,543	$ 203,608	(56,828)	420,427	706,563
Adjustment for basic earnings per share:
Earnings allocated to unvested shareholders									(1,858)	(2,163)	(4,132)
Numerator for basic earnings per share:
From continuing operations									(54,848)	418,311	702,478
From discontinued operations									(3,838)	(47)	(47)
Net income (loss) attributable to parent, basic									(58,686)	418,264	702,431
Adjustment for diluted earnings per share:
Effect of reallocating undistributed earnings of unvested shareholders										6	30
Numerator for diluted earnings per share:
From continuing operations									(54,848)	418,317	702,508
From discontinued operations									(3,838)	(47)	(47)
Net income (loss) attributable to parent, diluted									$ (58,686)	$ 418,270	$ 702,461
Denominator:
Denominator for basic earnings per share - weighted-average shares									107,996	107,754	107,800
Effect of dilutive shares from stock options and restricted stock (in shares)										816	1,341
Denominator for diluted earnings per share - adjusted weighted-average shares									107,996	108,570	109,141
Basic earnings per common share:
Income (loss) from continuing operations (in dollars per share)	$ (0.68)	$ (0.20)	$ 0.23	$ 0.15	$ (0.26)	$ 0.84	$ 1.42	$ 1.87	$ (0.50)	$ 3.88	$ 6.52
Loss from discontinued operations (in dollars per share)									(0.04)
Net income (loss) (in dollars per share)	(0.68)	(0.20)	0.19	0.15	(0.26)	0.84	1.42	1.87	(0.54)	3.88	6.52
Diluted earnings per common share:
Income (loss) from continuing operations (in dollars per share)	(0.68)	(0.20)	0.23	0.15	(0.26)	0.83	1.41	1.86	(0.50)	3.85	6.44
Loss from discontinued operations (in dollars per share)									(0.04)
Net income (loss) (in dollars per share)	$ (0.68)	$ (0.20)	$ 0.19	$ 0.15	$ (0.26)	$ 0.83	$ 1.41	$ 1.86	$ (0.54)	$ 3.85	$ 6.44
Outstanding equity awards
Shares excluded from calculation of diluted earnings per share									1,788	667	215
Weighted-average price per share (in dollars per share)									$ 63.73	$ 72.85	$ 79.67