CONSOLIDATED STATEMENTS OF INCOME - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Income Statement [Abstract]
Revenue	$ 274,727	$ 271,882	$ 842,063	$ 759,051
Cost of sales	152,973	156,492	470,525	429,508
Gross profit	121,754	115,390	371,538	329,543
Operating expenses:
Research, development and technical	12,165	12,191	38,206	39,009
Selling, general and administrative	51,847	50,959	162,495	162,415
Total operating expenses	64,012	63,150	200,701	201,424
Operating income	57,742	52,240	170,837	128,119
Interest expense	10,406	12,757	33,079	32,978
Interest income	131	417	589	2,004
Other income (expense), net	(201)	(472)	(1,608)	(2,897)
Income before income taxes	47,266	39,428	136,739	94,248
Provision for income taxes	12,741	20,550	30,766	34,790
Net income	$ 34,525	$ 18,878	$ 105,973	$ 59,458
Basic earnings per share (in dollars per share)	$ 1.19	$ 0.65	$ 3.63	$ 2.09
Diluted earnings per share (in dollars per share)	$ 1.17	$ 0.64	$ 3.58	$ 2.06
Weighted average basic shares outstanding (in shares)	29,079,000	29,064,000	29,157,000	28,399,000
Weighted average diluted shares outstanding (in shares)	29,456,000	29,568,000	29,603,000	28,924,000