Net Income (Loss) Per Share (Additional Information) (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net (loss) income	$ (13,510)	$ 77,332	$ 35,175	$ 96,422
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	(13,510)	(28,397)	41,367	(14,516)
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	$ 0	$ 105,729	$ (6,192)	$ 110,938
Weighted Average Number of Shares Outstanding, Basic	282,576	285,866	283,366	286,849
Dilutive Securities, Effect on Basic Earnings Per Share	0	0	4,848	0
Weighted Average Number of Shares Outstanding, Diluted	282,576	285,866	288,214	286,849
Earnings Per Share, Basic	$ (0.05)	$ 0.27	$ 0.12	$ 0.34
Discontinued Operation, Income (Loss) from Discontinued Operation, Net of Tax, Per Basic Share	0	0.37	(0.03)	0.39
Income (Loss) from Continuing Operations, Per Basic Share	$ (0.05)	$ (0.10)	$ 0.15	$ (0.05)
Weighted Average Number of Shares, Contingently Issuable	2,113	2,646	1,706	2,422
Income (Loss) from Continuing Operations, Per Diluted Share	$ (0.05)	$ (0.10)	$ 0.14	$ (0.05)
Discontinued Operation, Income (Loss) from Discontinued Operation, Net of Tax, Per Diluted Share	0	0.37	(0.02)	0.39
Earnings Per Share, Diluted	$ (0.05)	$ 0.27	$ 0.12	$ 0.34
Anti-dilutive common equivalent shares excluded from computation of diluted net income (loss) per share	73	460	39	635