Revenue (Schedule of Contract Liability) (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Sep. 30, 2020
Contract With Customer Liability [Line Items]
Current contract liabilities	$ 29,522	$ 24,620
Noncurrent contract liabilities	381,989	366,642
Deferred Revenue From Material Rights From GE Joint Venture Formation [Member]
Contract With Customer Liability [Line Items]
Current contract liabilities	4,595	4,066
Noncurrent contract liabilities	235,463	234,240
Deferred Revenue From Advance Invoicing And/Or Prepayments From Customers [Member]
Contract With Customer Liability [Line Items]
Current contract liabilities	3,227	3,239
Noncurrent contract liabilities	513	85
Liability Related To Customer Supplied Inventory [Member]
Contract With Customer Liability [Line Items]
Current contract liabilities	17,456	14,955
Deferred Revenue From Material Rights Related To Engineering And Development Funding [Member]
Contract With Customer Liability [Line Items]
Current contract liabilities	4,244	2,360
Noncurrent contract liabilities	$ 146,013	$ 132,317