Business Segment Information (Schedule Of Earnings Before Income Tax) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Mar. 31, 2012	Mar. 31, 2011
Segment Reporting Information [Line Items]
Consolidated EBIT	$ 17,074	$ 21,585	$ 25,907	$ 38,158
Less: Interest expense	(470)	(538)	(961)	(1,312)
Earnings before income taxes	16,604	21,047	24,946	36,846
USG [Member]
Segment Reporting Information [Line Items]
Consolidated EBIT	9,101	15,814	14,067	31,169
Test [Member]
Segment Reporting Information [Line Items]
Consolidated EBIT	4,775	5,214	6,722	7,123
Filtration [Member]
Segment Reporting Information [Line Items]
Consolidated EBIT	9,468	6,534	17,704	12,009
Corporate (Loss) [Member]
Segment Reporting Information [Line Items]
Consolidated EBIT	$ (6,270)	$ (5,977)	$ (12,586)	$ (12,143)