Accounting Policies (Comparison of Reported Condensed Consolidated Statement of Operations to the Pro-forma Amounts had the Previous U.S. GAAP Guidance been in Effect) (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Total revenue	$ 537,656	$ 462,021
Total cost of revenue	234,557	203,830
Gross profit	303,099	258,191
Income from operations	113,044	92,243
Interest expense	(9,274)	(8,589)
Interest income	579	1,083
Income before provision for income taxes	104,349	84,737
Provision for income taxes	14,873	15,679
Net income	89,476	$ 69,058
Accounting Standards Update 2014-09 [Member]
Total revenue	537,656
Total cost of revenue	234,557
Gross profit	303,099
Total operating expense	190,055
Income from operations	113,044
Interest expense	(9,274)
Interest income	579
Income before provision for income taxes	104,349
Provision for income taxes	14,873
Net income	89,476
Attributed to the New Revenue Standard [Member] | Accounting Standards Update 2014-09 [Member]
Total revenue	12,287
Total cost of revenue	6,592
Gross profit	5,695
Total operating expense	(571)
Income from operations	6,266
Interest income	(283)
Income before provision for income taxes	5,983
Provision for income taxes	1,444
Net income	4,539
Previous U.S. GAAP (Reported) [Member] | Accounting Standards Update 2014-09 [Member]
Total revenue	525,369
Total cost of revenue	227,965
Gross profit	297,404
Total operating expense	190,626
Income from operations	106,778
Interest expense	(9,274)
Interest income	862
Income before provision for income taxes	98,366
Provision for income taxes	13,429
Net income	$ 84,937