Contingencies - Warranty (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Standard product warranty length, minimum	1 year
Standard product warranty length, maximum	2 years
Limited product warranty length (up to)	10 years
Movement in Standard Product Warranty Accrual [Roll Forward]
Balance at beginning of period	$ 15,331	$ 18,091
Accruals for warranties issued	2,305	4,212
Changes in liability related to warranties existing in prior periods	(1,874)	(2,296)
Payments made	(2,330)	(4,191)
Balance at end of period	$ 13,432	$ 15,816