Income Taxes (Narrative) (Details) (USD $)	3 Months Ended	12 Months Ended
	Sep. 30, 2012	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2011
Income Tax Disclosure [Line Items]
Effective income tax rate		14.00%	(14.00%)	129.00%
Income before income taxes		$ 186,112,000	$ 126,234,000	$ 120,736,000
Statutory federal income tax rate		35.00%	35.00%	35.00%
Deferred tax assets, change in valuation allowance	124,500,000
Effective Income Tax Rate Reconciliation, Foreign Income Tax Withholding, Amount		5,100,000	6,000,000
Effective Income Tax Rate Reconciliation, Tax Settlement, Foreign, Amount			5,300,000
Effect of change in the tax status of the foreign legal entity				4,200,000
Effective income tax rate, one-time increase		0.00%	0.00%	3.00%
Tax provision related to research and development cost sharing prepayment		2,000,000		7,800,000
Deferred Tax Liabilities, Net		136,196,000	120,796,000
Prepaid income taxes		6,300,000	11,500,000
Income taxes payable		17,700,000	14,400,000
Accrued income taxes		9,300,000	7,100,000
Other current liabilities		1,300,000	2,100,000
Other liabilities		7,100,000	5,200,000
Income tax payments		25,500,000	35,400,000	53,000,000
Net deferred tax assets		2,802,000	4,400,000
Net operating loss carryforwards		97,200,000
Valuation allowance	170,400,000	177,541,000	156,547,000	170,400,000	38,600,000
Interest expense		300,000	(1,200,000)	300,000
Penalty expense		0		100,000
Interest expense related to income tax accruals		1,400,000	1,100,000
Accrued tax penalties			100,000
Unrecognized tax benefit	19,100,000	15,000,000	13,700,000	19,100,000	16,200,000
Income tax provision upon recognition of unrecognized tax benefit		13,800,000
Unrecognized tax benefits, increase in valuation allowance upon recognition		7,600,000
Unrecognized tax benefits, increase to additional paid-in capital upon recognition		1,200,000
Potential decrease in unrecognized tax benefits		2,000,000
Stock-based compensation		50,889,000	48,787,000	51,305,000
Tax benefit recognition related to stock based compensation		700,000	2,700,000	3,900,000
Increase (decrease) in income taxes payable		(19,134,000)	15,211,000	4,005,000
Windfall tax deductions not yet recognized		21,000,000
Undistributed Earnings of Foreign Subsidiaries		642,000,000	378,000,000
Deferred Tax Assets, Tax Credit Carryforwards, Foreign		9,022,000	5,994,000
Domestic Country [Member]
Income Tax Disclosure [Line Items]
Valuation allowance		144,000,000
Deferred Tax Assets, Tax Credit Carryforwards, Foreign		9,000,000
Domestic Country [Member] | Research Tax Credit Carryforward [Member]
Income Tax Disclosure [Line Items]
Credit carryforwards		17,700,000
Foreign Country [Member]
Income Tax Disclosure [Line Items]
Net operating loss carryforwards		187,300,000
Valuation allowance		33,500,000
Credit carryforwards		7,400,000
Japan [Member]
Income Tax Disclosure [Line Items]
Impact of a Japanese legislative change on our Japan entities' deferred tax assets				1,400,000
Windfall Tax Benefit [Member]
Income Tax Disclosure [Line Items]
Increase (decrease) in income taxes payable		10,400,000	300,000	1,100,000
Windfall tax deductions not yet recognized		21,000,000
Massachusetts Research And Development Member | Research Tax Credit Carryforward [Member]
Income Tax Disclosure [Line Items]
Credit carryforwards		21,300,000
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			38,672,000
All Acquisitions [Member]
Income Tax Disclosure [Line Items]
Net operating loss carryforwards		82,700,000
Axeda and ThingWorx [Member]
Income Tax Disclosure [Line Items]
Deferred tax assets, change in valuation allowance		(18,100,000)
Net operating loss carryforwards		63,500,000
Servigistics and Enigma [Member]
Income Tax Disclosure [Line Items]
Deferred tax assets, change in valuation allowance			(36,700,000)
Prior Acquisitions [Member]
Income Tax Disclosure [Line Items]
Net operating loss carryforwards		19,200,000
Deferred Tax Asset, Pension [Member]
Income Tax Disclosure [Line Items]
Deferred tax assets, change in valuation allowance		$ (7,900,000)