Summary of Significant Accounting Policies ASC 606 Impact, Balance Sheet (Details) - USD ($) $ in Thousands		12 Months Ended
	Oct. 01, 2018	Sep. 30, 2019	Sep. 30, 2018
ASC 606 Impact, Balance Sheet [Line Items]
Accounts Receivable, Net, Current		$ 308,601	$ 347,873
Prepaid expenses and other current assets		199,096	94,814
Other Assets, Noncurrent		351,581	141,761
Deferred Revenue, Current		302,872	330,689
Deferred Revenue, Noncurrent		398,834	434,316
Deferred Tax Liabilities, Net, Noncurrent		54,216	49,931
Other liabilities		100,981	93,593
Accumulated deficit		(293,612)	$ (740,837)
Accounts Receivable [Member]
ASC 606 Impact, Balance Sheet [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	$ 30,000	31,072
Prepaid Expenses and Other Current Assets
ASC 606 Impact, Balance Sheet [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification		(74,582)
Other Assets [Member]
ASC 606 Impact, Balance Sheet [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification		(129,760)
Deferred revenue, current [Domain]
ASC 606 Impact, Balance Sheet [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification		20,704
Deferred Revenue [Domain]
ASC 606 Impact, Balance Sheet [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification		16,122
Deferred Tax Asset [Domain]
ASC 606 Impact, Balance Sheet [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	$ 20,000	16,635
Other Noncurrent Liabilities [Member]
ASC 606 Impact, Balance Sheet [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification		(10,331)
Accumulated Deficit
ASC 606 Impact, Balance Sheet [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification		(181,496)
Pro Forma [Member]
ASC 606 Impact, Balance Sheet [Line Items]
Accounts Receivable, Net, Current		339,673
Prepaid expenses and other current assets		124,514
Other Assets, Noncurrent		221,821
Deferred Revenue, Current		323,576
Deferred Revenue, Noncurrent		414,956
Deferred Tax Liabilities, Net, Noncurrent		37,581
Other liabilities		90,650
Accumulated deficit		$ (475,108)