UNAUDITED CONSOLIDATED STATEMENTS OF INCOME - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
UNAUDITED CONSOLIDATED STATEMENTS OF INCOME [Abstract]
Revenue	$ 108,152	$ 97,168	$ 307,765	$ 313,960
Cost of goods sold	56,127	48,609	158,649	153,751
Gross profit	52,025	48,559	149,116	160,209
Operating expenses:
Research, development and technical	12,928	14,773	42,690	44,922
Selling and marketing	6,243	5,804	19,660	19,220
General and administrative	10,738	12,830	37,991	38,877
Total operating expenses	29,909	33,407	100,341	103,019
Operating income	22,116	15,152	48,775	57,190
Interest expense	1,178	1,065	3,536	3,030
Other income (expense), net	(246)	(160)	396	565
Income before income taxes	20,692	13,927	45,635	54,725
Provision for income taxes	1,990	4,041	6,493	11,112
Net income	$ 18,702	$ 9,886	$ 39,142	$ 43,613
Basic earnings per share (in dollars per share)	$ 0.78	$ 0.40	$ 1.62	$ 1.80
Weighted average basic shares outstanding (in shares)	23,928,512	24,332,879	24,022,809	24,004,885
Diluted earnings per share (in dollars per share)	$ 0.76	$ 0.39	$ 1.59	$ 1.75
Weighted average diluted shares outstanding (in shares)	24,325,166	24,813,462	24,402,880	24,654,853
Dividends per share (in dollars per share)	$ 0.18	$ 0	$ 0.36	$ 0