Net Income (Loss) Per Share (Additional Information) (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net (loss) income	$ 19,090	$ 53,228
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	17,699	47,465
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	$ 1,391	$ 5,763
Weighted Average Number of Shares Outstanding, Basic	287,796	291,367
Dilutive Securities, Effect on Basic Earnings Per Share	4,563	4,628
Weighted Average Number of Shares Outstanding, Diluted	292,359	295,995
Earnings Per Share, Basic	$ 0.07	$ 0.18
Discontinued Operation, Income (Loss) from Discontinued Operation, Net of Tax, Per Basic Share	0.01	0.02
Income (Loss) from Continuing Operations, Per Basic Share	$ 0.06	$ 0.16
Weighted Average Number of Shares, Contingently Issuable	2,076	2,252
Income (Loss) from Continuing Operations, Per Diluted Share	$ 0.06	$ 0.16
Discontinued Operation, Income (Loss) from Discontinued Operation, Net of Tax, Per Diluted Share	0.01	0.02
Earnings Per Share, Diluted	$ 0.07	$ 0.18
Anti-dilutive common equivalent shares excluded from computation of diluted net income (loss) per share	1,962	39