Accrued Expenses and Other Current Liabilities (Severance and Restructuring Accruals) (Narrative) (Details) $ in Millions	1 Months Ended		3 Months Ended	12 Months Ended
	Mar. 31, 2017 employee	Nov. 30, 2016 employee	Dec. 31, 2016 USD ($)	Sep. 30, 2018 employee	Sep. 30, 2017 USD ($)
Employee Severance [Member]
Payables and Accruals [Line Items]
Restructuring costs | $					$ 0.4
Satellite Communications Assembly Operations [Member] | Employee Severance [Member]
Payables and Accruals [Line Items]
Number of positions eliminated | employee		5
Restructuring costs | $			$ 0.2
Ivyland, Pennsylvania Location Closure [Member] | Employee Severance [Member]
Payables and Accruals [Line Items]
Restructuring costs | $					0.3
Water Fabrication Lab [Member]
Payables and Accruals [Line Items]
Number of positions eliminated | employee	14
Water Fabrication Lab [Member] | Employee Severance [Member]
Payables and Accruals [Line Items]
Number of positions eliminated | employee	72
Restructuring costs | $					0.1
Workforce Reduction [Member] | Employee Severance [Member]
Payables and Accruals [Line Items]
Number of positions eliminated | employee	6
Restructuring costs | $					0.4
New Manufacturing Facility in China [Member] | Employee Severance [Member]
Payables and Accruals [Line Items]
Number of positions eliminated | employee	265
Restructuring costs | $					$ 0.5
Scenario, Forecast [Member] | Ivyland, Pennsylvania Location Closure [Member] | Employee Severance [Member]
Payables and Accruals [Line Items]
Number of positions eliminated | employee				11