Goodwill and Intangible Assets - Intangible Assets (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Intangible Assets [Line Items]
Amortized intangible assets, gross carrying amount	$ 836,595	$ 756,936
Amortized intangible assets, accumulated amortization	(569,574)	(546,021)
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	455,998	410,680
Amortized intangible assets, accumulated amortization	(325,583)	(314,730)
Customer Lists and Contract Backlog
Intangible Assets [Line Items]
Amortized intangible assets, gross carrying amount	238,373	209,031
Amortized intangible assets, accumulated amortization	(127,770)	(117,614)
Trade Names
Intangible Assets [Line Items]
Amortized intangible assets, gross carrying amount	142,224	137,225
Amortized intangible assets, accumulated amortization	$ (116,221)	$ (113,677)