Income Taxes (Narrative) (Details)		3 Months Ended	12 Months Ended					60 Months Ended
		Jan. 03, 2015 USD ($)	Sep. 30, 2016 USD ($) foreign_subsidiary		Sep. 30, 2015 USD ($)		Sep. 30, 2014 USD ($) foreign_subsidiary	Sep. 30, 2015 USD ($)		Sep. 30, 2013 USD ($)
Income Tax Disclosure [Line Items]
Effective income tax rate			(19.00%)		(79.00%)		14.00%
Income before income taxes			$ (67,192,000)		$ 26,525,000		$ 186,112,000
Statutory federal income tax rate			(35.00%)		35.00%		35.00%
Effective Income Tax Rate Reconciliation, Other Adjustments, Amount			$ (28,000,000)		$ (24,000,000)
Decrease of valuation allowance in foreign jurisdictions			3,100,000
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Other, Amount					14,500,000
Pension valuation allowance					(18,700,000)
Deferred Other Tax Expense (Benefit)					(1,400,000)
Effective Income Tax Rate Reconciliation, Tax Credit, Research, Amount		$ 2,100,000	6,000,000
Effective Income Tax Rate Reconciliation, Foreign Income Tax Withholding, Amount					3,800,000		$ 5,100,000
Other Tax Expense (Benefit)					3,100,000
Change in foreign income tax withholding valuation allowance			$ 600,000		0		$ 3,500,000
Number of foreign subsidiaries included in valuation allowance | foreign_subsidiary			2				2
Prepaid income taxes			$ 9,900,000		8,200,000			$ 8,200,000
Income taxes payable			18,700,000		14,700,000			14,700,000
Accrued income taxes			6,300,000		4,000,000			4,000,000
Other current liabilities			5,500,000		2,200,000			2,200,000
Other liabilities			6,900,000		8,500,000			8,500,000
Income tax payments			25,500,000		30,100,000		$ 25,500,000
Net deferred tax assets	[1]		75,942,000		31,756,000			31,756,000
Net operating loss related to windfall tax deductions			45,100,000
Valuation allowance			235,503,000	[1]	198,168,000	[1]	177,500,000	198,168,000	[1]	$ 156,500,000
Interest expense			500,000		100,000		300,000
Penalty expense			0		0		0
Interest expense related to income tax accruals			2,000,000		1,500,000			1,500,000
Accrued tax penalties			0		0		0	0
Unrecognized tax benefit			15,500,000		14,100,000		15,000,000	14,100,000		$ 13,700,000
Income tax provision upon recognition of unrecognized tax benefit			(13,900,000)
Unrecognized tax benefits, increase in valuation allowance upon recognition			4,800,000
Unrecognized tax benefits, increase to additional paid-in capital upon recognition			1,600,000
Potential decrease in unrecognized tax benefits			8,000,000
Stock-based compensation			65,996,000		50,182,000		50,889,000
Tax benefit recognition related to stock based compensation			700,000		700,000		700,000
Increase (decrease) in income taxes payable			(6,749,000)		3,536,000		(19,134,000)
Expected deferred tax expense			12,000,000
Undistributed Earnings of Foreign Subsidiaries			789,000,000		684,000,000			684,000,000
Deferred Tax Assets, Tax Credit Carryforwards, Foreign	[1]		18,041,000		15,962,000			$ 15,962,000
R&D credit related to windfall tax deductions			14,000,000
Domestic Country [Member]
Income Tax Disclosure [Line Items]
Net operating loss carryforwards			247,100,000
Valuation allowance			209,000,000
Deferred Tax Assets, Tax Credit Carryforwards, Foreign			18,000,000
Domestic Country [Member] | Research Tax Credit Carryforward [Member]
Income Tax Disclosure [Line Items]
Credit carryforwards			25,200,000
State - Massachusetts [Member] | Research Tax Credit Carryforward [Member]
Income Tax Disclosure [Line Items]
Credit carryforwards			24,800,000
Foreign Country [Member]
Income Tax Disclosure [Line Items]
Net operating loss carryforwards			102,400,000
Valuation allowance			26,500,000
Credit carryforwards			$ 7,500,000
Korea
Income Tax Disclosure [Line Items]
Income Tax Examination, Description			12					12
Windfall Tax Benefit [Member]
Income Tax Disclosure [Line Items]
Increase (decrease) in income taxes payable			$ 100,000		$ 0		10,400,000
Windfall tax deductions not yet recognized			33,400,000
2014 Acquisitions [Member]
Income Tax Disclosure [Line Items]
Deferred tax assets, change in valuation allowance							(18,100,000)
Deferred Tax Liabilities, Net							$ 21,600,000
All Acquisitions [Member] | Domestic Country [Member]
Income Tax Disclosure [Line Items]
Net operating loss carryforwards			$ 82,200,000

[1] (1) See Note B. Recent Accounting Pronouncements-Deferred Taxes regarding a change in the balance sheet classification of our deferred taxes.