CONSOLIDATED STATEMENTS OF STOCKHOLDERS’ EQUITY - USD ($) shares in Thousands, $ in Thousands		Total	Common Stock	Additional Paid-In Capital	Treasury Stock	Accumulated Other Comprehensive Loss	Accumulated Deficit
Beginning balance (in shares) at Sep. 30, 2020			286,703		3,751
Beginning balance at Sep. 30, 2020		$ 1,143,933	$ 287	$ 1,550,568	$ (16,788)	$ (117,918)	$ (272,216)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under employee stock plans (in shares)			3,117
Issuance of common stock under employee stock plans		0	$ 3	(3)
Cancellation of restricted stock, and repurchase of common stock at cost for employee tax withholding (in shares)			(1,151)
Cancellation of restricted stock, and repurchase of common stock at cost for employee tax withholding		(43,703)	$ (1)	(43,702)
Stock-based compensation		75,455		75,455
Equity portion of convertible debt puttable		(53,343)		(53,343)
Net (loss) income		14,895					14,895
Other comprehensive income (loss)		15,799				15,799
Ending balance (in shares) at Dec. 31, 2020			288,669		3,751
Ending balance at Dec. 31, 2020		1,153,036	$ 289	1,528,975	$ (16,788)	(102,119)	(257,321)
Beginning balance (in shares) at Sep. 30, 2021			319,402		3,751
Beginning balance at Sep. 30, 2021		1,634,934	$ 319	2,054,994	$ (16,788)	(104,649)	(298,942)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under employee stock plans (in shares)			3,875
Issuance of common stock under employee stock plans		64	$ 4	60
Cancellation of restricted stock, and repurchase of common stock at cost for employee tax withholding (in shares)			(1,549)
Cancellation of restricted stock, and repurchase of common stock at cost for employee tax withholding		(85,375)	$ (1)	(85,374)
Stock-based compensation		81,361		81,361
Equity portion of convertible debt puttable		4,315		4,315
Redemption of Convertible Notes (in shares)	[1]		854
Redemption of Convertible Notes	[1]	(216)	$ 1	(217)
Net (loss) income		(57,559)					(57,559)
Other comprehensive income (loss)		(2,625)				(2,625)
Ending balance (in shares) at Dec. 31, 2021			322,582		3,751
Ending balance at Dec. 31, 2021		$ 1,574,899	$ 323	$ 2,055,139	$ (16,788)	$ (107,274)	$ (356,501)

[1] According to ASC 470-20, cash consideration paid to repurchase and retire our convertible notes was first allocated to debt component based on the actual fair value on the trading date, and the remaining consideration was allocated to additional paid-in capital.