Intangible Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Intangible Assets [Line Items]
Amortized intangible assets, gross carrying amount	$ 663,565	$ 626,095
Amortized intangible assets, accumulated amortization	(506,297)	(453,833)
Unamortized intangible assets, gross carrying amount	357
Developed Software and Core Technologies
Intangible Assets [Line Items]
Amortized intangible assets, gross carrying amount	365,317	338,594
Amortized intangible assets, accumulated amortization	(297,645)	(275,130)
Customer Lists and Contract Backlog
Intangible Assets [Line Items]
Amortized intangible assets, gross carrying amount	171,048	159,549
Amortized intangible assets, accumulated amortization	(104,522)	(88,414)
Trade Names
Intangible Assets [Line Items]
Amortized intangible assets, gross carrying amount	127,200	127,952
Amortized intangible assets, accumulated amortization	(104,130)	(90,289)
Trade Names
Intangible Assets [Line Items]
Unamortized intangible assets, gross carrying amount	$ 357	$ 357