Revenue (Schedule of Contract Liability) (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Sep. 30, 2023
Contract With Customer Liability [Line Items]
Current contract liabilities	$ 49,665	$ 33,748
Noncurrent contract liabilities	420,328	414,657
Deferred Revenue From Material Rights From GE Joint Venture Formation [Member]
Contract With Customer Liability [Line Items]
Current contract liabilities	6,472	6,147
Noncurrent contract liabilities	234,159	233,997
Deferred Revenue From Advance Invoicing And/Or Prepayments From Customers [Member]
Contract With Customer Liability [Line Items]
Current contract liabilities	18,454	6,868
Noncurrent contract liabilities	3,258	2,196
Liability Related To Customer Supplied Inventory [Member]
Contract With Customer Liability [Line Items]
Current contract liabilities	19,198	14,543
Deferred Revenue From Material Rights Related To Engineering And Development Funding [Member]
Contract With Customer Liability [Line Items]
Current contract liabilities	5,541	6,190
Noncurrent contract liabilities	$ 182,911	$ 178,464