Income Taxes (Narrative) (Details)	3 Months Ended	12 Months Ended
	Jan. 03, 2015 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($) foreign_subsidiary	Sep. 30, 2013 USD ($)	Sep. 30, 2012 USD ($)
Income Tax Disclosure [Line Items]
Effective income tax rate		(79.00%)	14.00%	(14.00%)
Income before income taxes		$ 26,525,000	$ 186,112,000	$ 126,234,000
Statutory federal income tax rate		35.00%	35.00%	35.00%
Effective Income Tax Rate Reconciliation, Other Adjustments, Amount		$ (24,000,000)
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)
Effective Income Tax Rate Reconciliation, Foreign Income Tax Withholding, Amount		3,800,000	$ 5,100,000	$ 6,000,000
Other Tax Expense (Benefit)		3,100,000
Change in foreign income tax withholding valuation allowance		0	$ 3,500,000	0
Number of foreign subsidiaries included in valuation allowance | foreign_subsidiary			2
Effective Income Tax Rate Reconciliation, Tax Settlement, Foreign, Amount				(5,300,000)
Tax provision related to research and development cost sharing prepayment				2,000,000	$ 7,800,000
Prepaid income taxes		8,200,000	$ 6,300,000
Income taxes payable		14,700,000	17,700,000
Accrued income taxes		4,000,000	9,300,000
Other current liabilities		2,200,000	1,300,000
Other liabilities		8,500,000	7,100,000
Income tax payments		30,100,000	25,500,000	35,400,000
Net deferred tax assets		31,756,000	2,802,000
Net operating loss related to windfall tax deductions		38,800,000
Valuation allowance		198,168,000	177,541,000	156,500,000	170,400,000
Interest expense		100,000	300,000	(1,200,000)
Penalty expense		0		0
Interest expense related to income tax accruals		1,500,000	1,400,000
Accrued tax penalties		0	0	100,000
Unrecognized tax benefit		14,100,000	15,000,000	13,700,000	$ 19,100,000
Income tax provision upon recognition of unrecognized tax benefit		(12,500,000)
Unrecognized tax benefits, increase in valuation allowance upon recognition		4,500,000
Unrecognized tax benefits, increase to additional paid-in capital upon recognition		1,600,000
Potential decrease in unrecognized tax benefits		4,000,000
Stock-based compensation		50,182,000	50,889,000	48,787,000
Tax benefit recognition related to stock based compensation		700,000	700,000	2,700,000
Increase (decrease) in income taxes payable		3,536,000	(19,134,000)	15,211,000
Expected deferred tax expense		11,000,000
Undistributed Earnings of Foreign Subsidiaries		1,915,000,000	613,000,000
Deferred Tax Assets, Tax Credit Carryforwards, Foreign		15,962,000	9,022,000
Domestic Country [Member]
Income Tax Disclosure [Line Items]
Net operating loss carryforwards		159,700,000
Valuation allowance		166,500,000
Deferred Tax Assets, Tax Credit Carryforwards, Foreign		16,000,000
Domestic Country [Member] | Research Tax Credit Carryforward [Member]
Income Tax Disclosure [Line Items]
Credit carryforwards		18,500,000
Foreign Country [Member]
Income Tax Disclosure [Line Items]
Net operating loss carryforwards		117,700,000
Valuation allowance		31,700,000
Credit carryforwards		7,200,000
Windfall Tax Benefit [Member]
Income Tax Disclosure [Line Items]
Increase (decrease) in income taxes payable		0	10,400,000	300,000
Windfall tax deductions not yet recognized		30,100,000
Massachusetts Research And Development Member | Research Tax Credit Carryforward [Member]
Income Tax Disclosure [Line Items]
Credit carryforwards		25,700,000
2014 Acquisitions [Member]
Income Tax Disclosure [Line Items]
Deferred Tax Liabilities, Net			21,600,000
Servigistics, Enigma and NetIDEAS [Member]
Income Tax Disclosure [Line Items]
Deferred Tax Liabilities, Net				38,700,000
All Acquisitions [Member] | Domestic Country [Member]
Income Tax Disclosure [Line Items]
Net operating loss carryforwards		$ 81,000,000
Axeda and ThingWorx [Member]
Income Tax Disclosure [Line Items]
Deferred tax assets, change in valuation allowance			$ (18,100,000)
Servigistics and Enigma [Member]
Income Tax Disclosure [Line Items]
Deferred tax assets, change in valuation allowance				(36,700,000)
Deferred Tax Asset, Pension [Member]
Income Tax Disclosure [Line Items]
Deferred tax assets, change in valuation allowance				$ (7,900,000)