Fair Value Measurement (Narrative) (Details) - USD ($) $ in Thousands	6 Months Ended
	Apr. 01, 2017	Apr. 02, 2016	Sep. 30, 2016	Sep. 30, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration related to acquisitions	$ 16,668		$ 19,570
Payment of contingent consideration	3,100	$ 1,300
Business Combination, Consideration Transferred, Liabilities Incurred	2,700
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration related to acquisitions	16,668	29,190	$ 19,570	$ 13,000
Payment of contingent consideration	3,050	$ 1,250
Fair Value, Inputs, Level 3 [Member] | 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	12,000
Fair Value, Inputs, Level 3 [Member] | Other Noncurrent Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration related to acquisitions	$ 4,700