Acquisitions Recognized Amounts of Identifiable Assets Acquired and Liabilities Assumed 2019 (Details) - USD ($)	Dec. 31, 2019	Nov. 01, 2019	Feb. 01, 2019
Business Acquisition [Line Items]
Cash	$ 28,395,000
Accounts receivable and other tangible assets	38,255,000
Indemnification asset	34,039,000
Accounts payable and other liabilities	(16,860,000)
Deferred revenue	(6,880,000)
Uncertain tax positions	(34,296,000)
Net deferred tax liabilities	(65,712,000)
Total identifiable net assets	280,993,000
Goodwill	841,771,000
Developed Software and Core Technologies
Business Acquisition [Line Items]
Finite-lived intangible assets	225,163,000
Customer Lists
Business Acquisition [Line Items]
Finite-lived intangible assets	61,659,000
Trade Names
Business Acquisition [Line Items]
Finite-lived intangible assets	17,230,000
Livermore Software Technology Corporation
Business Acquisition [Line Items]
Cash		$ 8,520,000
Accounts receivable and other tangible assets		20,568,000
Indemnification asset		34,039,000
Accounts payable and other liabilities		(3,721,000)
Deferred revenue		(3,565,000)
Uncertain tax positions		(34,039,000)
Net deferred tax liabilities		(47,596,000)
Total identifiable net assets		178,406,000
Goodwill		599,390,000
Livermore Software Technology Corporation | Developed Software and Core Technologies
Business Acquisition [Line Items]
Finite-lived intangible assets		167,700,000
Livermore Software Technology Corporation | Customer Lists
Business Acquisition [Line Items]
Finite-lived intangible assets		25,900,000
Livermore Software Technology Corporation | Trade Names
Business Acquisition [Line Items]
Finite-lived intangible assets		$ 10,600,000
Granta Design
Business Acquisition [Line Items]
Cash			$ 13,644,000
Accounts receivable and other tangible assets			6,941,000
Indemnification asset			0
Accounts payable and other liabilities			(6,714,000)
Deferred revenue			(1,426,000)
Uncertain tax positions			0
Net deferred tax liabilities			(9,822,000)
Total identifiable net assets			59,663,000
Goodwill			149,073,000
Granta Design | Developed Software and Core Technologies
Business Acquisition [Line Items]
Finite-lived intangible assets			32,445,000
Granta Design | Customer Lists
Business Acquisition [Line Items]
Finite-lived intangible assets			20,016,000
Granta Design | Trade Names
Business Acquisition [Line Items]
Finite-lived intangible assets			$ 4,579,000
Other Acquisitions
Business Acquisition [Line Items]
Cash	6,231,000
Accounts receivable and other tangible assets	10,746,000
Indemnification asset	0
Accounts payable and other liabilities	(6,425,000)
Deferred revenue	(1,889,000)
Uncertain tax positions	(257,000)
Net deferred tax liabilities	(8,294,000)
Total identifiable net assets	42,924,000
Goodwill	93,308,000
Other Acquisitions | Developed Software and Core Technologies
Business Acquisition [Line Items]
Finite-lived intangible assets	25,018,000
Other Acquisitions | Customer Lists
Business Acquisition [Line Items]
Finite-lived intangible assets	15,743,000
Other Acquisitions | Trade Names
Business Acquisition [Line Items]
Finite-lived intangible assets	$ 2,051,000