Recently Issued Accounting Standards (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018
Recently Issued Accounting Pronouncements
Cost of goods sold	$ 112,791	$ 96,693	$ 208,525	$ 177,311
Nonoperating retirement benefit expense	$ 856	2,083	$ 1,712	4,171
Reclassification upon adoption | ASU 2017-07
Recently Issued Accounting Pronouncements
Cost of goods sold		(2,100)		(4,200)
Nonoperating retirement benefit expense		$ 2,100		$ 4,200