Revenue - Disaggregated Revenue (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disaggregation Of Revenue [Line Items]
Total revenues	$ 121,333	$ 108,556	$ 106,625
Online [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	121,333	108,388	101,827
IT Deal Alert [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	59,049	49,529	31,404
Core Online [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	62,284	58,859	70,423
Events [Member]
Disaggregation Of Revenue [Line Items]
Total revenues		168	4,798
North America [Member] | Online [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	82,660	73,208	69,039
North America [Member] | IT Deal Alert [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	43,342	36,622	25,743
North America [Member] | Core Online [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	39,318	36,586	43,296
International [Member] | Online [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	38,673	35,180	32,788
International [Member] | IT Deal Alert [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	15,707	12,907	5,661
International [Member] | Core Online [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	$ 22,966	$ 22,273	$ 27,127