Business Segment Information (Schedule Of Net Sales And Earnings Before Income Tax) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Segment Reporting Information [Line Items]
Net sales	$ 169,449	$ 176,326	$ 496,237	$ 503,010
Consolidated EBIT	20,063	20,751	45,970	58,909
Less: Interest expense	(916)	(534)	(1,877)	(1,846)
Earnings before income taxes	19,147	20,217	44,093	57,063
USG [Member]
Segment Reporting Information [Line Items]
Net sales	76,683	86,837	221,507	264,018
Consolidated EBIT	12,962	12,428	27,029	43,597
Test [Member]
Segment Reporting Information [Line Items]
Net sales	41,815	45,848	131,652	119,955
Consolidated EBIT	2,395	4,616	9,117	11,739
Filtration [Member]
Segment Reporting Information [Line Items]
Net sales	50,951	43,641	143,078	119,037
Consolidated EBIT	11,228	9,595	28,932	21,604
Corporate (Loss) [Member]
Segment Reporting Information [Line Items]
Consolidated EBIT	$ (6,522)	$ (5,888)	$ (19,108)	$ (18,031)