CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-in-Capital	(Accumulated Deficit) Retained Earnings	Net Parent Investment	Accumulated Other Comprehensive Income (Loss)
Balance at Sep. 30, 2019	$ 1,068,128				$ 1,097,127	$ (28,999)
Net income (loss)	(26,523)			$ (26,523)
Other comprehensive income	5,034					5,034
Distribution to Parent	(152,978)				(152,978)
Net (decrease) increase in net parent investment	11,453				(4,275)	15,728
Reclassification of net parent investment in Cerence			$ 939,874		(939,874)
Issuance of common stock at separation		$ 364	(364)
Issuance of common stock at separation, (in shares)		36,391
Issuance of common stock	2	$ 2
Issuance of common stock, (in shares)		207
Stock withheld to cover tax withholdings requirements upon stock vesting	(1,615)	$ 0	(1,615)
Stock withheld to cover tax withholdings requirements upon restricted stock vesting, (in shares)		(78)
Convertible Senior Notes conversion feature	14,369		14,369
Stock-based compensation	21,748		21,748
Balance at Jun. 30, 2020	939,618	$ 366	974,012	(26,523)		(8,237)
Balance (in shares) at Jun. 30, 2020		36,520
Balance at Sep. 30, 2019	1,068,128				$ 1,097,127	(28,999)
Net income (loss)	(18,316)
Balance at Sep. 30, 2020	960,071	$ 369	974,307	(18,316)		3,711
Balance (in shares) at Sep. 30, 2020		36,842
Balance at Mar. 31, 2020	937,175	$ 365	949,916	1,529		(14,635)
Balance (in shares) at Mar. 31, 2020		36,458
Net income (loss)	(28,052)			(28,052)
Other comprehensive income	6,398					6,398
Issuance of common stock	1	$ 1
Issuance of common stock, (in shares)		96
Stock withheld to cover tax withholdings requirements upon stock vesting	(696)		(696)
Stock withheld to cover tax withholdings requirements upon restricted stock vesting, (in shares)		(34)
Convertible Senior Notes conversion feature	14,369		14,369
Stock-based compensation	10,423		10,423
Balance at Jun. 30, 2020	939,618	$ 366	974,012	(26,523)		(8,237)
Balance (in shares) at Jun. 30, 2020		36,520
Balance at Sep. 30, 2020	960,071	$ 369	974,307	(18,316)		3,711
Balance (in shares) at Sep. 30, 2020		36,842
Net income (loss)	37,902			37,902
Other comprehensive income	5,868					5,868
Issuance of common stock	6,682	$ 14	6,668
Issuance of common stock, (in shares)		1,441
Stock withheld to cover tax withholdings requirements upon stock vesting	(34,089)	$ (4)	(34,085)
Stock withheld to cover tax withholdings requirements upon restricted stock vesting, (in shares)		(455)
Stock-based compensation	45,415		45,415
Balance at Jun. 30, 2021	1,021,849	$ 379	992,305	19,586		9,579
Balance (in shares) at Jun. 30, 2021		37,828
Balance at Mar. 31, 2021	1,003,441	$ 379	983,640	13,788		5,634
Balance (in shares) at Mar. 31, 2021		37,780
Net income (loss)	5,798			5,798
Other comprehensive income	3,945					3,945
Issuance of common stock	1,637		1,637
Issuance of common stock, (in shares)		51
Stock withheld to cover tax withholdings requirements upon stock vesting	(1,889)		(1,889)
Stock withheld to cover tax withholdings requirements upon restricted stock vesting, (in shares)		(3)
Stock-based compensation	8,917		8,917
Balance at Jun. 30, 2021	$ 1,021,849	$ 379	$ 992,305	$ 19,586		$ 9,579
Balance (in shares) at Jun. 30, 2021		37,828