Fair Value Measurement (Narrative) (Details) - USD ($) $ in Thousands	6 Months Ended		27 Months Ended
	Mar. 31, 2018	Apr. 01, 2017	Mar. 31, 2018	Sep. 30, 2017	Sep. 30, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration related to acquisitions	$ 6,743		$ 6,743	$ 8,400
Payment of contingent consideration	3,800	$ 3,100
Business Combination, Consideration Transferred, Liabilities Incurred	3,200	2,700
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration related to acquisitions	6,743	16,668	6,743	8,400	$ 19,570
Payment of contingent consideration	3,757	3,050
Level 3 | Accrued Expenses and Other Current Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration related to acquisitions	5,700		5,700
Level 3 | Other Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration related to acquisitions	1,100		1,100
Kepware
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration related to acquisitions	4,600		4,600
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, High	18,000		18,000
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, Low	16,900		16,900
payment of contingent consideration			13,400
Kepware | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration related to acquisitions	4,643	15,418	$ 4,643	$ 8,400	$ 17,070
Payment of contingent consideration	$ 3,757	$ 1,800