Balance Sheet Details (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Sep. 30, 2019	Dec. 31, 2018
Restricted Cash
Restricted cash	$ 32,400		$ 29,500
Accounts Receivable
Allowance for doubtful accounts	(1,407)	$ (1,392)
Current accounts receivable	112,086	126,014
Inventories
Finished products	11,167	10,905
Work in process and inventoried costs under long-term contracts	67,075	46,951
Materials and purchased parts	44,670	48,938
Net inventories	122,912	106,794
Costs incurred outside the scope of work or in advance of a contract award	4,800	5,800
General and administrative amounts for certain government contracts remaining in inventory	500	500
Property, Plant and Equipment
Accumulated depreciation and amortization	(168,247)	(160,271)
Property, plant and equipment - net	151,218	144,969
Deferred Compensation Plan
Deferred compensation	11,800	11,000
Carrying value of Rabbi trust to fund deferred compensation liabilities	6,800	6,800
U.S. federal government contracts
Accounts Receivable
Billed	23,300		$ 60,300
Land and land improvements
Property, Plant and Equipment
Property, plant and equipment, Gross	7,463	7,348
Buildings and improvements
Property, Plant and Equipment
Property, plant and equipment, Gross	49,359	48,191
Machinery and other equipment
Property, Plant and Equipment
Property, plant and equipment, Gross	119,674	107,297
Software
Property, Plant and Equipment
Property, plant and equipment, Gross	107,513	108,526
Leasehold improvements
Property, Plant and Equipment
Property, plant and equipment, Gross	17,671	17,064
Construction and internal-use software development in progress
Property, Plant and Equipment
Property, plant and equipment, Gross	$ 17,785	$ 16,814