Summary Of Significant Accounting Policies (Narrative) (Details)	12 Months Ended
	Sep. 30, 2018 USD ($) primary_source mo	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Oct. 01, 2017 USD ($)	Sep. 30, 2015 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Payment of contingent consideration	$ 8,925,000	$ 12,100,000
Maximum payment terms on software purchases for credit-worthy customers (in months) | mo	24
Subscription revenue, number of primary sources | primary_source	2
Cloud services revenue percent of total revenue	5.00%	5.00%	5.00%
Cost Method Investments	$ 1,700,000	$ 700,000
Proceeds from sale of cost method investments		13,700,000
Gain on sale of cost-method investments		3,700,000
Allowance for doubtful accounts receivable	600,000	1,100,000	$ 1,000,000		$ 1,000,000
Accounts receivable written-off, net of recoveries	1,000,000	1,500,000	300,000
Bad debt expense including general and administrative expense	500,000	1,500,000	300,000
Development costs for software	0	0	0
Capitalized software in connection with acquisition	800,000	6,000,000
Advertising expense	2,900,000	2,500,000	2,100,000
Cumulative translation adjustment gains (loss)	66,400,000	(54,600,000)
Pension benefits, before tax	27,000,000	24,700,000
Pension benefits net of tax	19,200,000	17,600,000
Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Before Tax	(400,000)	1,800,000
Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Effect Net of Tax	(400,000)	1,500,000
Accumulated Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	(400,000)	(100,000)
Deferred Tax Assets, Other	1,152,000	6,599,000
Allowance for Sales Credits	2,000,000
Deferred Revenue	$ 499,443,000	458,907,000
Minimum [Member] | Computer Hardware And Software [Member]
Summary Of Significant Accounting Policies [Line Items]
Amortization period (in years)	3 years
Minimum [Member] | Furniture And Fixtures [Member]
Summary Of Significant Accounting Policies [Line Items]
Amortization period (in years)	3 years
Maximum [Member] | Purchased Software [Member]
Summary Of Significant Accounting Policies [Line Items]
Amortization period (in years)	11 years
Maximum [Member] | Customer Lists [Member]
Summary Of Significant Accounting Policies [Line Items]
Amortization period (in years)	12 years
Maximum [Member] | Trademarks And Trade Names [Member]
Summary Of Significant Accounting Policies [Line Items]
Amortization period (in years)	12 years
Maximum [Member] | Computer Hardware And Software [Member]
Summary Of Significant Accounting Policies [Line Items]
Amortization period (in years)	5 years
Maximum [Member] | Furniture And Fixtures [Member]
Summary Of Significant Accounting Policies [Line Items]
Amortization period (in years)	8 years
Foreign Exchange Forward [Member]
Summary Of Significant Accounting Policies [Line Items]
Derivative maturity (in months)	3 months
Designated as Hedging Instrument [Member] | Foreign Exchange Forward [Member]
Summary Of Significant Accounting Policies [Line Items]
Derivative, Remaining Maturity	14 months
Accounting Standards Update 2016-16 [Member]
Summary Of Significant Accounting Policies [Line Items]
Deferred Tax Assets, Other	$ 72,000,000
Accounting Standards Update 2016-09 [Member]
Summary Of Significant Accounting Policies [Line Items]
Windfall tax deductions not yet recognized				$ 37,000,000
Windfall Tax Deductions Not Yet Recognized Offset Valuation Allowance				36,900,000
Excess Tax Benefit from Share-based Compensation, Operating Activities		600,000	100,000
Excess tax benefits realized from stock-based awards		$ 600,000	$ 100,000
Forfeiture adjustment				$ 700,000
Accounting Standards Update 2014-09 [Member]
Summary Of Significant Accounting Policies [Line Items]
Commissions	70,000,000
Accounting Standards Update 2014-09 [Member] | Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Deferred Revenue	350,000,000
Accounting Standards Update 2014-09 [Member] | Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Deferred Revenue	$ 380,000,000