Revenue from Contracts with Customers (Additional Information) (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017	Oct. 01, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Contract with Customer, Asset, Reclassified to Receivable	$ 17,800
Contract with Customer, Asset, Additions during Period	13,800
Deferred Revenue, Revenue Recognized	333,700
Deferred Revenue, Additions	374,100
Short Term and Long Term Accounts Receivable	412,500			$ 503,700
Contract with Customer, Refund Liability	22,900
Contract asset	21,038			25,037
Deferred revenue	396,632			356,263
Billed but uncollected support and subscription-related revenue	185,700	$ 153,600
Revenue	1,255,631	1,241,824	$ 1,164,039
Accounting Standards Update 2014-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of new accounting principle		363,218
Accounting Standards Update 2014-09 [Member] | Retained Earnings [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect Of New Accounting Principle In Period Of Adoption, Gross				432,200
Cumulative effect of new accounting principle		363,218		363,200
Cumulative Effect Of New Accounting Principle In Period Of Adoption, Related To Deferral Of Commission Expenses				70,000
Cumulative Effect Of New Accounting Principle In Period Of Adoption, Related To Offsetting Current Liability				2,800
Other Current Assets [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Capitalized Contract Cost, Net	27,700
Other Assets
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Capitalized Contract Cost, Net	64,800
Restatement Adjustment [Member] | Accounting Standards Update 2014-09 [Member] | Retained Earnings [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect Of New Accounting Principle In Period Of Adoption, Gross				300
Cumulative effect of new accounting principle				4,200
Previously Reported [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Contract asset				26,200
Deferred revenue				357,500
Previously Reported [Member] | Accounting Standards Update 2014-09 [Member] | Retained Earnings [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect Of New Accounting Principle In Period Of Adoption, Gross				431,900
Cumulative effect of new accounting principle				367,400
License
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue	324,400	529,265	356,326
License | Accounting Standards Update 2014-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue	215,000
Revenue on new and renewal bookings	153,500
Germany [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue	185,400	193,300	164,700
United States [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue	$ 514,400	$ 487,300	$ 475,500
Revenue from Contract with Customer Benchmark [Member] | Accounting Standards Update 2014-09 [Member] | Retained Earnings [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of new accounting principle				366,800
Revenue from Contract with Customer Benchmark [Member] | Deferred Revenue [Member] | Accounting Standards Update 2014-09 [Member] | Retained Earnings [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of new accounting principle				143,200
Revenue from Contract with Customer Benchmark [Member] | Other Assets | Accounting Standards Update 2014-09 [Member] | Retained Earnings [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of new accounting principle				5,100
Unbilled Contracts Receivables [Member] | Revenue from Contract with Customer Benchmark [Member] | Accounting Standards Update 2014-09 [Member] | Retained Earnings [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of new accounting principle				$ 218,500