Revenues (Disaggregation of Revenue) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Disaggregation of Revenue [Line Items]
Total revenues	$ 307,142	$ 315,068
Point in time
Disaggregation of Revenue [Line Items]
Total revenues	11,522	8,983
Over time
Disaggregation of Revenue [Line Items]
Total revenues	295,620	306,085
Operating Segments
Disaggregation of Revenue [Line Items]
Total revenues	307,142	315,068
Operating Segments | Digital Media
Disaggregation of Revenue [Line Items]
Total revenues	234,211	234,827
Operating Segments | Cybersecurity and Martech
Disaggregation of Revenue [Line Items]
Total revenues	73,016	80,494
Operating Segments | Advertising | Digital Media
Disaggregation of Revenue [Line Items]
Total revenues	156,082	170,067
Operating Segments | Subscription | Digital Media
Disaggregation of Revenue [Line Items]
Total revenues	69,148	55,576
Operating Segments | Subscription | Cybersecurity and Martech
Disaggregation of Revenue [Line Items]
Total revenues	73,016	80,494
Operating Segments | Other | Digital Media
Disaggregation of Revenue [Line Items]
Total revenues	8,981	9,184
Elimination of inter-segment revenues
Disaggregation of Revenue [Line Items]
Total revenues	$ (85)	$ (253)