Business Segment Information - Geographic Information Net Sales (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Net Sales	$ 208,030	$ 172,665	$ 180,492	$ 171,728	$ 213,177	$ 178,259	$ 171,243	$ 163,365	$ 732,915	$ 726,044	$ 683,650
United States
Net Sales									531,861	537,200	495,800
Asia
Net Sales									96,300	86,200	92,600
Europe
Net Sales									51,300	45,000	41,300
Canada
Net Sales									31,700	33,000	30,200
India
Net Sales									10,300	11,700	9,400
Other
Net Sales									$ 11,400	$ 12,900	$ 14,400