Consolidated Statements of Stockholders' Deficit - USD ($) $ in Millions	Common stock	Additional paid in capital	Accumulated other comprehensive income	Accumulated deficit	Total
Balance at Sep. 30, 2017		$ 323.5	$ 53.1	$ (378.9)	$ (2.3)
Balance, shares at Sep. 30, 2017	20,402,602
Foreign currency translation adjustments			0.2		0.2
Actuarial gains/losses on pension plan			5.2		5.2
Change in fair value of hedging instrument			0.3		0.3
Reclassification of gain on hedging instrument to comprehensive income			(0.3)		(0.3)
Shares issued on exercise of warrants
Shares issued on exercise of warrants, shares	50
Shares of RSAs that vested and shares issued upon net settlement of RSUs		(1.1)			(1.1)
Shares of RSAs that vested and shares issued upon net settlement of RSUs, shares	457,939
Reclassification of RSUs from derivative liability due to stockholder approval of equity plan		2.8			2.8
Stock-based compensation expense		4.8			4.8
Reclassification of RSUs to derivative liability due to modification		(1.5)			(1.5)
Net loss				(20.6)	(20.6)
Balance at Sep. 30, 2018		328.5	58.5	(399.5)	(12.5)
Balance, shares at Sep. 30, 2018	20,860,591
Actuarial gains/losses on pension plan			(2.8)		(2.8)
Change in fair value of hedging instrument			2.6		2.6
Reclassification of gain on hedging instrument to comprehensive income			(2.4)		(2.4)
Shares issued upon net settlement of RSUs
Shares issued upon net settlement of RSUs, shares	9,806
Stock-based compensation expense		1.4			1.4
Net loss				(4.7)	(4.7)
Balance at Dec. 31, 2018		329.9	55.9	(404.2)	(18.4)
Balance, shares at Dec. 31, 2018	20,870,397
Foreign currency translation adjustments			(2.4)		(2.4)
Actuarial gains/losses on pension plan			(6.9)		(6.9)
Change in fair value of hedging instrument			2.9		2.9
Reclassification of gain on hedging instrument to comprehensive income			(4.4)		(4.4)
Conversion of awards previously classified as derivatives		0.8			0.8
Shares issued in earnout		8.6			8.6
Shares issued in earnout, shares	1,323,558
Shares issued upon net settlement of RSUs		(0.9)			(0.9)
Shares issued upon net settlement of RSUs, shares	36,813
Stock-based compensation expense		8.2			8.2
Net loss				(37.0)	(37.0)
Balance at Dec. 31, 2019		$ 346.6	$ 45.1	$ (441.2)	$ (49.5)
Balance, shares at Dec. 31, 2019	22,230,768