Income Taxes (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Jan. 03, 2015	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Income Tax Disclosure [Line Items]
Effective Income Tax Rate Reconciliation, Foreign Income Tax Rate Differential, Amount		$ (27,932)	$ (27,513)	$ (56,375)
Decrease of valuation allowance in foreign jurisdictions		(9,000)	(3,100)
Effective Income Tax Rate Reconciliation, Resolution of Uncertain Tax Positions, Amount		(3,840)	0	(2,991)
Effective Income Tax Rate Reconciliation, Foreign Income Tax Withholding, Amount		2,737	1,987	3,764
Effective Income Tax Rate Reconciliation, Tax Credit, Research, Amount	$ 2,100	2,182	5,981	2,097
Tax permanent items related to pending legal settlement				14,500
Pension valuation allowance				(18,700)
Other Tax Expense (Benefit)				3,100
Deferred Other Tax Expense (Benefit)				(1,400)
Income taxes payable		16,200	18,700
Accrued income taxes		5,700	6,300
Other current liabilities		2,300	5,500
Prepaid income taxes		7,100	9,900
Other liabilities		8,200	6,900
Income tax payments		35,400	25,500	30,100
Net operating loss related to windfall tax deductions		61,400
Deferred Tax Assets, Tax Credit Carryforwards, Foreign		21,099	18,041
R&D credit related to windfall tax deductions		13,400
Gross Deferred Interest Carryforward		93,300
Gross Deferred Amortization Carryforward		535,600
Valuation allowance		279,683	235,503	198,200	$ 177,500
Interest expense		900	500	100
Penalty expense		0	0	0
Interest expense related to income tax accruals		1,100	2,000
Accrued tax penalties		0	0	0
Unrecognized tax benefit		14,800	15,500	14,100	$ 15,000
Income tax provision upon recognition of unrecognized tax benefit		14,800
Unrecognized tax benefits, increase in valuation allowance upon recognition		5,100
Potential decrease in unrecognized tax benefits		6,000
Stock-based compensation		76,708	65,996	50,182
Tax benefit recognition related to stock based compensation		1,300	700	700
Increase (decrease) in income taxes payable		798	(6,749)	3,536
Deferred Tax Liability Not Recognized, Description of Temporary Difference, Undistributed Earnings of Foreign Subsidiaries		(11,440)	(67)
Expected deferred tax expense		12,000
Undistributed Earnings of Foreign Subsidiaries		882,000	789,000
realignment [Member]
Income Tax Disclosure [Line Items]
Effective Income Tax Rate Reconciliation, Foreign Income Tax Rate Differential, Amount		(28,000)	(28,000)	(24,000)
foreign jurisdiction [Member]
Income Tax Disclosure [Line Items]
Effective Income Tax Rate Reconciliation, Resolution of Uncertain Tax Positions, Amount		(3,500)
Domestic Country [Member]
Income Tax Disclosure [Line Items]
Net operating loss carryforwards		383,000
Deferred Tax Assets, Tax Credit Carryforwards, Foreign		20,800
Valuation allowance		239,300
Domestic Country [Member] | Research Tax Credit Carryforward [Member]
Income Tax Disclosure [Line Items]
Credit carryforwards		27,400
State - Massachusetts [Member] | Research Tax Credit Carryforward [Member]
Income Tax Disclosure [Line Items]
Credit carryforwards		23,500
Foreign Country [Member]
Income Tax Disclosure [Line Items]
Net operating loss carryforwards		90,200
Credit carryforwards		5,400
Valuation allowance		40,400
Korea
Income Tax Disclosure [Line Items]
Income Tax Examination, Estimate of Possible Loss		12,000
Windfall Tax Benefit [Member]
Income Tax Disclosure [Line Items]
Increase (decrease) in income taxes payable		600	100	$ 0
Windfall tax deductions not yet recognized		38,300
All Acquisitions [Member] | Domestic Country [Member]
Income Tax Disclosure [Line Items]
Net operating loss carryforwards		82,200
Patents [Member]
Income Tax Disclosure [Line Items]
Effective Income Tax Rate Reconciliation, Foreign Income Tax Withholding, Amount		$ 2,000	$ 2,000