Intangible Assets (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Intangible Assets [Line Items]
Amortized intangible assets, gross carrying amount	$ 666,249	$ 663,565
Amortized intangible assets, accumulated amortization	(520,210)	(506,297)
Indefinite-lived intangible assets (excluding goodwill)	357
Trade Names
Intangible Assets [Line Items]
Indefinite-lived intangible assets (excluding goodwill)	357	357
Developed Software and Core Technologies
Intangible Assets [Line Items]
Amortized intangible assets, gross carrying amount	365,684	365,317
Amortized intangible assets, accumulated amortization	(303,026)	(297,645)
Customer Lists and Contract Backlog
Intangible Assets [Line Items]
Amortized intangible assets, gross carrying amount	173,250	171,048
Amortized intangible assets, accumulated amortization	(109,438)	(104,522)
Trade Names
Intangible Assets [Line Items]
Amortized intangible assets, gross carrying amount	127,315	127,200
Amortized intangible assets, accumulated amortization	$ (107,746)	$ (104,130)