Business Segment Information (Schedule Of Net Sales And Earnings Before Income Tax) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2013 segment	Mar. 31, 2012
Segment Reporting Information [Line Items]
Number of reporting segments			3
Net sales	$ 166,178	$ 173,863	$ 311,443	$ 326,788
Consolidated EBIT	4,213	17,074	5,073	25,907
Less: Interest expense	(668)	(470)	(1,231)	(961)
Earnings before income taxes	3,545	16,604	3,842	24,946
USG [Member]
Segment Reporting Information [Line Items]
Net sales	72,731	74,475	135,349	144,824
Consolidated EBIT	(2,423)	9,101	(4,631)	14,067
Test [Member]
Segment Reporting Information [Line Items]
Net sales	39,821	50,483	76,116	89,837
Consolidated EBIT	2,559	4,775	3,078	6,722
Filtration [Member]
Segment Reporting Information [Line Items]
Net sales	53,626	48,905	99,978	92,127
Consolidated EBIT	10,894	9,468	19,695	17,704
Corporate (Loss) [Member]
Segment Reporting Information [Line Items]
Consolidated EBIT	$ (6,817)	$ (6,270)	$ (13,069)	$ (12,586)