Capital Assets (Goodwill) (Details) $ in Thousands	6 Months Ended
Mar. 31, 2018 USD ($)
Goodwill [Roll Forward]
Balance, September 30, 2017	$ 369,762
Currency translation	751
Balance, March 31, 2018	370,513
Test
Goodwill [Roll Forward]
Balance, September 30, 2017	25,109
Currency translation	715
Balance, March 31, 2018	25,824
Sensors
Goodwill [Roll Forward]
Balance, September 30, 2017	344,653
Currency translation	36
Balance, March 31, 2018	$ 344,689

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13770-109266

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=64834752&loc=SL49117168-202975

Name:	us-gaap_Goodwill
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant