Business Segment Information - Capital Expenditures (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Capital Expenditures	$ 32,108	$ 24,229	$ 15,243
Corporate
Capital Expenditures	200	0	0
Aerospace & Defense
Capital Expenditures	15,900	11,700	7,000
USG
Capital Expenditures	12,400	8,500	5,200
Test
Capital Expenditures	$ 3,600	$ 4,000	$ 3,000