Basis of Presentation (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 30, 2019 USD ($)	Mar. 31, 2018 USD ($)	Mar. 30, 2019 USD ($) Segment	Mar. 31, 2018 USD ($)	Dec. 29, 2018 USD ($)	Oct. 01, 2018 USD ($)	Sep. 30, 2018 USD ($)	Dec. 30, 2017 USD ($)	Sep. 30, 2017 USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of operating segments | Segment			2
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity Attributable to Parent	$ 1,247,708	$ 927,724	$ 1,247,708	$ 927,724	$ 1,321,169		$ 874,589	$ 889,099	$ 885,436
Deferred tax assets	195,884		195,884				165,566
Other income (expense), net	821	(285)	1,475	(1,083)
Accounting Standards Update 2016-16
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred tax assets						$ 75,300
Other Tax Assets						6,000
Other Tax Liabilities						3,000
Accounting Standards Update 2017-07
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other income (expense), net		200		300
Accumulated Deficit
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity Attributable to Parent	(182,298)	$ (629,597)	(182,298)	$ (629,597)	$ (138,785)		(599,409)	$ (637,519)	$ (650,840)
Accumulated Deficit | Accounting Standards Update 2016-16
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity Attributable to Parent						$ 72,300
Other Current Assets
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Restricted Cash	$ 1,100		$ 1,100				$ 1,100