Income Taxes (Narrative) (Details) (USD $)	0 Months Ended	3 Months Ended	12 Months Ended				3 Months Ended	12 Months Ended
	Jan. 31, 2010	Apr. 30, 2011	Oct. 31, 2011	Oct. 31, 2010	Oct. 31, 2009	Oct. 31, 2010 Avant! Corporation [Member]	Jan. 31, 2011 Synplicity, Inc. [Member]	Oct. 31, 2010 Increase Net [Member]
Income Taxes [Line Items]
Decrease in valuation allowance			$ 1,300,000
Unrecognized deferred tax assets			36,800,000
Undistributed foreign earnings			530,000,000
Tax on deferred undistributed foreign earnings			114,000,000
Decrease in gross unrecognized tax benefits			36,000,000
Gross unrecognized tax benefits			177,893,000	213,923,000	253,861,000
Unrecognized tax benefits affecting effective tax rate			177,000,000	202,000,000
The sum of the amounts of estimated penalties and interest recognized in the period arising from income tax examinations			2,800,000	3,400,000	2,000,000
The amount of estimated penalties and interest accrued as of the balance sheet date arising from income tax examinations			7,400,000	7,300,000
Estimated potential decrease in underlying unrecognized tax benefits, minimum			0
Estimated potential decrease in underlying unrecognized tax benefits, maximum			110,000,000
Income tax examination years	audit of its fiscal years 2002 through 2004	IRS for its audits of fiscal years 2006 through 2009		audit of its fiscal years 2002 through 2004				audit of its fiscal years 2002 through 2004
Decrease in unrecognized tax benefits resulting from settlement with the IRS			(1,258,000)	(14,962,000)		67,800,000	4,000,000
Unrecognized tax benefits decreases resulting from settlements with US taxing authorities		35,900,000
Tax impact of final settlement with IRS		32,800,000				94,300,000
Release of valuation allowance						21,600,000
Tax adjustments settlements and unusual provisions				72,300,000				55,400,000
Decrease in deferred tax assets due to utilization of foreign tax credit carryover net of reversal of valuation allowance				$ 25,200,000
Penalties imposed on the amount of additional tax			50.00%