UNAUDITED CONSOLIDATED STATEMENTS OF INCOME - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
UNAUDITED CONSOLIDATED STATEMENTS OF INCOME [Abstract]
Revenue	$ 150,437	$ 127,957	$ 433,394	$ 370,395
Cost of goods sold	69,737	65,414	203,635	186,316
Gross profit	80,700	62,543	229,759	184,079
Operating expenses:
Research, development and technical	13,059	14,333	38,578	41,819
Selling and marketing	6,207	7,346	18,833	22,166
General and administrative	19,504	13,953	56,218	41,148
Total operating expenses	38,770	35,632	113,629	105,133
Operating income	41,930	26,911	116,130	78,946
Interest expense	513	1,117	2,803	3,402
Other income (expense), net	1,627	(115)	3,361	1,115
Income before income taxes	43,044	25,679	116,688	76,659
Provision for income taxes	7,873	5,740	54,863	16,209
Net income	$ 35,171	$ 19,939	$ 61,825	$ 60,450
Basic earnings per share (in dollars per share)	$ 1.37	$ 0.79	$ 2.42	$ 2.42
Weighted average basic shares outstanding (in shares)	25,611,505	25,228,468	25,479,078	24,941,190
Diluted earnings per share (in dollars per share)	$ 1.34	$ 0.77	$ 2.35	$ 2.37
Weighted average diluted shares outstanding (in shares)	26,318,638	25,720,715	26,221,864	25,449,507
Dividends per share (in dollars per share)	$ 0.40	$ 0.20	$ 1.00	$ 0.58