Balance Sheet Details (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Oct. 01, 2018	Sep. 30, 2018
Accounts Receivable
Billed	$ 180,594		$ 180,594			$ 156,948
Unbilled						242,877
Allowance for doubtful accounts	(1,745)		(1,745)			(1,324)
Total accounts receivable	178,849		178,849			398,501
Less estimated amounts not currently due						(6,134)
Current accounts receivable	178,849		178,849		$ 155,624	392,367
Sale of Trade Receivables	25,000
Inventories
Finished products	12,745		12,745			7,099
Work in process and inventoried costs under long-term contracts	73,838		73,838			63,169
Materials and purchased parts	37,714		37,714			23,710
Customer advances						(9,779)
Net inventories	124,297		124,297		61,688	84,199
Costs incurred outside the scope of work or in advance of a contract award	2,500		2,500			900
Property, Plant and Equipment
Accumulated depreciation and amortization	(129,638)		(129,638)			(144,782)
Property, plant and equipment - net	137,004		137,004		$ 117,546	117,546
Proceeds from sale of property, plant and equipment	44,891		44,891
Gain on sale of fixed assets	32,563		32,563
Deferred Compensation Plan
Deferred compensation	11,100		11,100			11,500
Carrying value of Rabbi trust to fund deferred compensation liabilities	6,300		6,300			6,300
Land and land improvements
Property, Plant and Equipment
Property, plant and equipment, Gross	9,611		9,611			13,132
Buildings and improvements
Property, Plant and Equipment
Property, plant and equipment, Gross	$ 32,343		$ 32,343			57,959
Lease term	5 years		5 years
Machinery and other equipment
Property, Plant and Equipment
Property, plant and equipment, Gross	$ 94,447		$ 94,447			81,727
Software
Property, Plant and Equipment
Property, plant and equipment, Gross	94,821		$ 94,821			84,631
Capitalized Software
Estimated useful life			seven-year
Addition to capitalized software expenses	100	$ 1,900	$ 700	$ 6,500
Software development expense	300	$ 2,800	$ 1,300	$ 13,100
Software | Maximum
Capitalized Software
Estimated useful life			seven years
Software | Minimum
Capitalized Software
Estimated useful life			three
Leasehold improvements
Property, Plant and Equipment
Property, plant and equipment, Gross	17,351		$ 17,351			11,991
Construction and internal-use software development in progress
Property, Plant and Equipment
Property, plant and equipment, Gross	$ 18,069		$ 18,069			$ 12,888