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, 2014	Mar. 31, 2013	Mar. 31, 2014	Mar. 31, 2013
Segment Reporting Information [Line Items]
Net sales	$ 124,762	$ 118,039	$ 249,212	$ 228,557
Consolidated EBIT	13,868	11,173	28,300	19,776
Less: Interest expense	(654)	(636)	(1,346)	(1,219)
Earnings before income taxes	13,214	10,537	26,954	18,557
Filtration [Member]
Segment Reporting Information [Line Items]
Net sales	58,397	53,626	113,875	99,977
Consolidated EBIT	10,100	10,894	19,584	19,695
Test [Member]
Segment Reporting Information [Line Items]
Net sales	41,025	39,821	80,503	76,116
Consolidated EBIT	3,533	2,559	7,108	3,078
USG [Member]
Segment Reporting Information [Line Items]
Net sales	25,340	24,592	54,834	52,464
Consolidated EBIT	5,518	4,149	13,165	9,603
Corporate (loss) [Member]
Segment Reporting Information [Line Items]
Consolidated EBIT	$ (5,283)	$ (6,429)	$ (11,557)	$ (12,600)

Sum of operating profit and nonoperating income or expense before Income or Loss from equity method investments, income taxes, extraordinary items, and noncontrolling interest.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.4-08.(h)(1)(i))

-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

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- Definition

This element represents the income or loss from continuing operations (before interest income and interest expense) attributable to the economic entity which may also be defined as revenue less expenses from ongoing operations, after income or loss from equity method investments, but before interest income, interest expense, income taxes, extraordinary items, and noncontrolling interest.

+ References

No definition available.

+ Details

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- Definition

The net amount of operating interest income (expense).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 225

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-04.10)

-URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph 10

-Article 9

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- Definition

Total revenue from sale of goods and services rendered during the reporting period, in the normal course of business, reduced by sales returns and allowances, and sales discounts.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.1)

-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 1

-Article 5

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- Details

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