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Recognized Amounts of Identifiable Assets Acquired and Liabilities Assumed (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Business Combination, Separately Recognized Transactions [Line Items]
Goodwill	$ 1,332,348	$ 1,312,182	$ 1,255,704
SpaceClaim Corporation [Member]
Business Combination, Separately Recognized Transactions [Line Items]
Cash	723
Accounts receivable and other tangible assets	1,857
Deferred tax assets	9,288
Accounts payable and other liabilities	(2,011)
Deferred revenue	(700)
Total identifiable net assets	36,507
Goodwill	48,453
SpaceClaim Corporation [Member] \| Developed Software
Business Combination, Separately Recognized Transactions [Line Items]
Finite-lived intangibles	15,800
SpaceClaim Corporation [Member] \| Customer Relationships
Business Combination, Separately Recognized Transactions [Line Items]
Finite-lived intangibles	9,400
SpaceClaim Corporation [Member] \| Trade Names
Business Combination, Separately Recognized Transactions [Line Items]
Finite-lived intangibles	1,300
SpaceClaim Corporation [Member] \| Contract Backlog
Business Combination, Separately Recognized Transactions [Line Items]
Finite-lived intangibles	550
SpaceClaim Corporation [Member] \| Non-Compete Agreements
Business Combination, Separately Recognized Transactions [Line Items]
Finite-lived intangibles	$ 300