UNAUDITED CONSOLIDATED STATEMENTS OF INCOME - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
UNAUDITED CONSOLIDATED STATEMENTS OF INCOME [Abstract]
Revenue	$ 127,957	$ 108,152	$ 370,395	$ 307,765
Cost of goods sold	65,414	56,127	186,316	158,649
Gross profit	62,543	52,025	184,079	149,116
Operating expenses:
Research, development and technical	14,333	12,928	41,819	42,690
Selling and marketing	7,346	6,243	22,166	19,660
General and administrative	13,953	10,738	41,148	37,991
Total operating expenses	35,632	29,909	105,133	100,341
Operating income	26,911	22,116	78,946	48,775
Interest expense	1,117	1,178	3,402	3,536
Other income (expense), net	(115)	(246)	1,115	396
Income before income taxes	25,679	20,692	76,659	45,635
Provision for income taxes	5,740	1,990	16,209	6,493
Net income	$ 19,939	$ 18,702	$ 60,450	$ 39,142
Basic earnings per share (in dollars per share)	$ 0.79	$ 0.78	$ 2.42	$ 1.62
Weighted average basic shares outstanding (in shares)	25,228,468	23,928,512	24,941,190	24,022,809
Diluted earnings per share (in dollars per share)	$ 0.77	$ 0.76	$ 2.37	$ 1.59
Weighted average diluted shares outstanding (in shares)	25,720,715	24,325,166	25,449,507	24,402,880
Dividends per share (in dollars per share)	$ 0.20	$ 0.18	$ 0.58	$ 0.36