Revenues (Disaggregation of Revenue) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Disaggregation of Revenue [Line Items]
Total revenues	$ 340,985	$ 341,873	$ 974,143	$ 994,297
Point in time
Disaggregation of Revenue [Line Items]
Total revenues	14,336	14,417	37,518	32,602
Over time
Disaggregation of Revenue [Line Items]
Total revenues	326,649	327,456	936,625	961,695
Operating Segments | Digital Media
Disaggregation of Revenue [Line Items]
Total revenues	267,951	263,896	755,032	757,423
Operating Segments | Cybersecurity and Martech
Disaggregation of Revenue [Line Items]
Total revenues	73,051	78,192	219,263	237,596
Operating Segments | Advertising | Digital Media
Disaggregation of Revenue [Line Items]
Total revenues	183,008	186,921	514,173	546,186
Operating Segments | Subscription | Digital Media
Disaggregation of Revenue [Line Items]
Total revenues	71,858	64,780	209,167	179,257
Operating Segments | Subscription | Cybersecurity and Martech
Disaggregation of Revenue [Line Items]
Total revenues	73,051	78,192	219,263	237,596
Operating Segments | Other | Digital Media
Disaggregation of Revenue [Line Items]
Total revenues	13,085	12,195	31,692	31,980
Elimination of inter-segment revenues
Disaggregation of Revenue [Line Items]
Total revenues	$ (17)	$ (215)	$ (152)	$ (722)