Revenues (Disaggregation of Revenue) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Disaggregation of Revenue [Line Items]
Total revenues	$ 341,873	$ 355,144	$ 994,297	$ 1,008,094
Point in time
Disaggregation of Revenue [Line Items]
Total revenues	14,417	13,607	32,602	30,669
Over time
Disaggregation of Revenue [Line Items]
Total revenues	327,456	341,537	961,695	977,425
Operating Segments
Disaggregation of Revenue [Line Items]
Total revenues	341,873	355,144	994,297	1,008,094
Operating Segments | Digital Media
Disaggregation of Revenue [Line Items]
Total revenues	263,896	262,429	757,423	743,280
Operating Segments | Cybersecurity and Martech
Disaggregation of Revenue [Line Items]
Total revenues	78,192	93,071	237,596	265,580
Operating Segments | Advertising | Digital Media
Disaggregation of Revenue [Line Items]
Total revenues	186,921	198,794	546,186	574,465
Operating Segments | Subscription | Digital Media
Disaggregation of Revenue [Line Items]
Total revenues	64,780	52,010	179,257	145,935
Operating Segments | Subscription | Cybersecurity and Martech
Disaggregation of Revenue [Line Items]
Total revenues	78,192	93,071	237,596	265,580
Operating Segments | Other | Digital Media
Disaggregation of Revenue [Line Items]
Total revenues	12,195	11,625	31,980	22,880
Elimination of inter-segment revenues
Disaggregation of Revenue [Line Items]
Total revenues	$ (215)	$ (356)	$ (722)	$ (766)