CONSOLIDATED STATEMENTS OF INCOME - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Income Statement [Abstract]
Revenue	$ 284,193	$ 265,391	$ 567,336	$ 487,169
Cost of sales	163,091	150,571	317,552	273,016
Gross profit	121,102	114,820	249,784	214,153
Operating expenses:
Research, development and technical	13,230	12,778	26,041	26,818
Selling, general and administrative	56,209	50,328	110,648	111,456
Total operating expenses	69,439	63,106	136,689	138,274
Operating income	51,663	51,714	113,095	75,879
Interest Expense	10,753	13,331	22,673	20,221
Interest income	143	568	458	1,587
Other income (expense), net	(1,010)	(1,014)	(1,407)	(2,425)
Income before income taxes	40,043	37,937	89,473	54,820
Provision for income taxes	7,144	10,800	18,025	14,240
Net income	$ 32,899	$ 27,137	$ 71,448	$ 40,580
Basic earnings per share (in dollars per share)	$ 1.12	$ 0.94	$ 2.45	$ 1.45
Diluted earnings per share (in dollars per share)	$ 1.11	$ 0.92	$ 2.41	$ 1.42
Weighted average basic shares outstanding (in shares)	29,287,211	28,997,632	29,182,528	28,065,759
Weighted average diluted shares outstanding (in shares)	29,725,179	29,479,114	29,666,436	28,607,033