Revenue (Schedule of Contract Liability) (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Sep. 30, 2020
Contract With Customer Liability [Line Items]
Current contract liabilities	$ 29,527	$ 24,620
Noncurrent contract liabilities	386,324	366,642
Deferred Revenue From Material Rights From GE Joint Venture Formation [Member]
Contract With Customer Liability [Line Items]
Current contract liabilities	4,771	4,066
Noncurrent contract liabilities	234,237	234,240
Deferred Revenue From Advance Invoicing And/Or Prepayments From Customers [Member]
Contract With Customer Liability [Line Items]
Current contract liabilities	4,192	3,239
Noncurrent contract liabilities	290	85
Liability Related To Customer Supplied Inventory [Member]
Contract With Customer Liability [Line Items]
Current contract liabilities	14,169	14,955
Deferred Revenue From Material Rights Related To Engineering And Development Funding [Member]
Contract With Customer Liability [Line Items]
Current contract liabilities	6,395	2,360
Noncurrent contract liabilities	$ 151,797	$ 132,317