Goodwill and Other Intangible Assets - Summary of Major Intangible Assets (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Intangible Assets Excluding Goodwill [Line Items]
Acquired Cost	$ 960,554	$ 953,644
Accumulated Amortization	(635,292)	(583,623)
Net Intangible Assets	325,262	370,021
Client Relationships [Member]
Intangible Assets Excluding Goodwill [Line Items]
Acquired Cost	654,892	649,494
Accumulated Amortization	(472,926)	(440,163)
Net Intangible Assets	181,966	209,331
Technology & Patents [Member]
Intangible Assets Excluding Goodwill [Line Items]
Acquired Cost	178,951	178,027
Accumulated Amortization	(107,634)	(96,774)
Net Intangible Assets	71,317	81,253
Trade Names and Trademarks [Member]
Intangible Assets Excluding Goodwill [Line Items]
Acquired Cost	103,437	103,398
Accumulated Amortization	(36,071)	(30,470)
Net Intangible Assets	67,366	72,928
Other Intangible Assets [Member]
Intangible Assets Excluding Goodwill [Line Items]
Acquired Cost	23,274	22,725
Accumulated Amortization	(18,661)	(16,216)
Net Intangible Assets	$ 4,613	$ 6,509