CONSOLIDATED STATEMENTS OF STOCKHOLDERS’ EQUITY - USD ($) $ in Thousands		Total	Common Stock	Additional Paid-In Capital	Treasury Stock	Accumulated Other Comprehensive Loss	Accumulated Deficit	Noncontrolling Interests
Beginning balance (in shares) at Sep. 30, 2019			289,680,000		3,751,000
Beginning balance at Sep. 30, 2019		$ 2,173,150	$ 290	$ 2,597,889	$ (16,788)	$ (132,773)	$ (293,612)	$ 18,144
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cerence spin-off		(928,380)		(922,567)		12,331		(18,144)
Issuance of common stock under employee stock plans (in shares)			7,194,000
Issuance of common stock under employee stock plans		7,270	$ 7	7,263
Cancellation of restricted stock, and repurchase of common stock at cost for employee tax withholding (in shares)			(2,292,000)
Cancellation of restricted stock, and repurchase of common stock at cost for employee tax withholding		(40,117)	$ (2)	(40,115)
Stock-based compensation		$ 110,644		110,644
Repurchase and retirement of common stock (in shares)		(9,500,000)	(9,457,000)
Repurchase and retirement of common stock		$ (169,218)	$ (10)	(169,208)
Equity portion of convertible debt puttable	[1]	(46,121)		(46,121)
Net (loss) income		45,341					45,341
Other comprehensive income		(2,240)				(2,240)
Ending balance (in shares) at Jun. 30, 2020			285,125,000		3,751,000
Ending balance at Jun. 30, 2020		1,150,329	$ 285	1,537,785	$ (16,788)	(122,682)	(248,271)	0
Beginning balance (in shares) at Mar. 31, 2020			284,832,000		3,751,000
Beginning balance at Mar. 31, 2020		1,109,221	$ 285	1,520,734	$ (16,788)	(130,077)	(264,933)	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under employee stock plans (in shares)			474,000
Issuance of common stock under employee stock plans		10	$ 0	10
Cancellation of restricted stock, and repurchase of common stock at cost for employee tax withholding (in shares)			(181,000)
Cancellation of restricted stock, and repurchase of common stock at cost for employee tax withholding		(3,510)		(3,510)
Stock-based compensation		20,551		20,551
Net (loss) income		16,662					16,662
Other comprehensive income		7,395				7,395
Ending balance (in shares) at Jun. 30, 2020			285,125,000		3,751,000
Ending balance at Jun. 30, 2020		1,150,329	$ 285	1,537,785	$ (16,788)	(122,682)	(248,271)	$ 0
Beginning balance (in shares) at Sep. 30, 2020			286,703,000		3,751,000
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)			4,892,000
Issuance of common stock under employee stock plans		8,368	$ 5	8,363
Cancellation of restricted stock, and repurchase of common stock at cost for employee tax withholding (in shares)			(1,703,000)
Cancellation of restricted stock, and repurchase of common stock at cost for employee tax withholding		(72,537)	$ (2)	(72,535)
Stock-based compensation		$ 117,599		117,599
Repurchase and retirement of common stock (in shares)		0
Equity portion of convertible debt puttable		$ (55,462)		(55,462)
Redemption of Convertible Notes (in shares)	[1]		25,604,000
Redemption of Convertible Notes	[1]	498,015	$ 25	497,990
Net (loss) income		(15,006)					(15,006)
Other comprehensive income		14,583				14,583
Ending balance (in shares) at Jun. 30, 2021			315,496,000		3,751,000
Ending balance at Jun. 30, 2021		1,639,493	$ 315	2,046,523	$ (16,788)	(103,335)	(287,222)
Beginning balance (in shares) at Mar. 31, 2021			289,248,000		3,751,000
Beginning balance at Mar. 31, 2021		1,121,852	$ 289	1,507,519	$ (16,788)	(108,213)	(260,955)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under employee stock plans (in shares)			1,130,000
Issuance of common stock under employee stock plans		0	$ 1	(1)
Cancellation of restricted stock, and repurchase of common stock at cost for employee tax withholding (in shares)			(486,000)
Cancellation of restricted stock, and repurchase of common stock at cost for employee tax withholding		(25,762)	$ 0	(25,762)
Stock-based compensation		20,906		20,906
Equity portion of convertible debt puttable		45,871		45,871
Redemption of Convertible Notes (in shares)	[1]		25,604,000
Redemption of Convertible Notes	[1]	498,015	$ 25	497,990
Net (loss) income		(26,267)					(26,267)
Other comprehensive income		4,878				4,878
Ending balance (in shares) at Jun. 30, 2021			315,496,000		3,751,000
Ending balance at Jun. 30, 2021		$ 1,639,493	$ 315	$ 2,046,523	$ (16,788)	$ (103,335)	$ (287,222)

[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.