Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Numerator:
Income (loss) from continuing operations	$ 500,642	$ (34,554)
Loss from discontinued operations	(536)	(509)
NET INCOME (LOSS)	500,106	(35,063)
Adjustment for basic earnings per share:
Earnings allocated to unvested shareholders	(3,537)	(446)
Numerator for basic earnings per share:
From continuing operations	497,105	(35,000)
From discontinued operations	(536)	(509)
Net income (loss) attributable to parent, basic	496,569	(35,509)
Adjustment for diluted earnings per share:
Effect of reallocating undistributed earnings of unvested shareholders	10
Numerator for diluted earnings per share:
From continuing operations	497,115	(35,000)
From discontinued operations	(536)	(509)
Net income (loss) attributable to parent, diluted	$ 496,579	$ (35,509)
Denominator:
Denominator for basic earnings per share – weighted-average shares	108,683	108,276
Effect of dilutive shares from stock options and restricted stock (in shares)	412
Denominator for diluted earnings per share – adjusted weighted-average shares	109,095	108,276
Basic earnings per common share:
Income (loss) from continuing operations (in dollars per share)	$ 4.57	$ (0.33)
Net income (loss) (in dollars per share)	4.57	(0.33)
Diluted earnings per common share:
Income (loss) from continuing operations (in dollars per share)	4.55	(0.33)
Net income (loss) (in dollars per share)	$ 4.55	$ (0.33)
Outstanding equity awards
Shares excluded from calculation of diluted earnings per share (in shares)	3,377	555
Weighted-average price per share (in dollars per share)	$ 63.47	$ 80.63