Accounts Receivable (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Sep. 30, 2016
Components of accounts receivable under long-term contracts
Total accounts receivable	$ 434,265	$ 388,345
Less estimated amounts not currently due	(17,457)	(20,926)
Accounts receivable under long-term contracts, current	416,808	367,419
U.S. government contracts
Components of accounts receivable under long-term contracts
Amounts billed	76,451	66,668
Recoverable costs and accrued profits on progress completed--not billed	88,105	81,624
Total accounts receivable	164,556	148,292
Commercial customers
Components of accounts receivable under long-term contracts
Amounts billed	119,041	79,955
Recoverable costs and accrued profits on progress completed--not billed	150,668	160,098
Total accounts receivable	$ 269,709	$ 240,053