Discontinued Operations - Financial Results (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Discontinued Operations and Disposal Groups [Abstract]
Revenues		$ 48,782
Cost of revenues		24,795
Sales and marketing		1,030
General and administrative		7,026
Total costs and operating expenses		32,851
Income from operations of discontinued operations		15,931
Interest expense and other, net		(1,286)
Income from discontinued operations before income taxes		14,645
Income tax expense		(4,604)
Gain on sale of discontinued operations, net of tax	$ 0	2,351	$ 0
Net income from discontinued operations, net of tax	$ 0	$ 12,392	$ 0