Accounts Receivable (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Sep. 30, 2017
Components of accounts receivable under long-term contracts
Total accounts receivable	$ 399,825	$ 371,933
Less estimated amounts not currently due	(6,134)	(17,457)
Accounts receivable under long-term contracts, current	393,691	354,476
U.S. government contracts
Components of accounts receivable under long-term contracts
Amounts billed	80,547	53,450
Recoverable costs and accrued profits on progress completed--not billed	62,665	36,341
Total accounts receivable	143,212	89,791
Commercial customers
Components of accounts receivable under long-term contracts
Amounts billed	76,401	131,532
Recoverable costs and accrued profits on progress completed--not billed	180,212	150,610
Total accounts receivable	$ 256,613	$ 282,142