Total Revenues Gross Profit and Long Lived Assets Excluding Long Term Deferred Tax Assets (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Revenues from External Customers and Long-Lived Assets
Total revenues	$ 120,602	$ 119,220	$ 243,569	$ 241,452
Gross profit	95,562	94,845	193,344	193,945
Long-lived assets	59,030		59,030		$ 63,269
Domestic
Revenues from External Customers and Long-Lived Assets
Total revenues	68,025	73,238	140,104	148,802
Gross profit	53,239	58,107	110,290	119,162
Long-lived assets	50,722		50,722		55,355
EMEA
Revenues from External Customers and Long-Lived Assets
Total revenues	38,008	34,024	76,206	67,752
Gross profit	30,246	27,023	60,761	54,229
Long-lived assets	5,595		5,595		5,626
Other Regions
Revenues from External Customers and Long-Lived Assets
Total revenues	14,569	11,958	27,259	24,898
Gross profit	12,077	$ 9,715	22,293	$ 20,554
Long-lived assets	$ 2,713		$ 2,713		$ 2,288