Income and Other Taxes (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Operating Loss Carryforwards [Line Items]
Income tax (expense) benefit	$ 87	$ 14	$ (55)	$ 14	$ 10	$ 14	$ 15	$ 15	$ 60	$ 54	$ (449)
Effective tax rate on continuing operations									1.00%	0.20%	(2.50%)
Portion of operating loss carryforward subject to limitation	236,100								$ 236,100
Portion of operating loss carryforward not subject to limitation	241,800								241,800
Interest and penalties accrued as tax liabilities	600				$ 500				600	$ 500
Foreign Income And Research And Development Credit [Member]
Operating Loss Carryforwards [Line Items]
Tax credit	2,700								2,700
Internal Revenue Service (IRS) [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	477,900								477,900
Foreign Tax Authority [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	6,700								6,700
State and Local Jurisdiction [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	$ 68,500								$ 68,500