Segment Information (Detail) - Reconciliation of Segment Gross Contribution to Net Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Costs and expenses:
Cost of services and product development	$ 945,648	$ 839,076	$ 797,933
Selling, general and administrative	1,089,184	962,677	876,067
Acquisition and integration charges	42,598	26,175	21,867
Operating income	305,141	287,997	286,162
Interest expense and other	16,710	15,786	11,479
Provision for income taxes	94,849	96,576	90,917
Net income	193,582	175,635	183,766
Operating Segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Total segment gross contribution	1,512,000	1,334,547	1,234,229
Corporate and Reconciling Items
Costs and expenses:
Cost of services and product development	13,108	10,567	10,721
Selling, general and administrative	1,089,184	962,677	876,067
Depreciation and amortization	61,969	47,131	39,412
Acquisition and integration charges	$ 42,598	$ 26,175	$ 21,867