Segment Information (Reconciliation of Total Segment Operating Income to Consolidated Operating Income) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Segment Reporting Information [Line Items]
Revenues	$ 307,142	$ 315,068
Operating expenses	280,827	284,506
Operating income	26,315	30,562
Reportable segments
Segment Reporting Information [Line Items]
Revenues	307,142	315,068
Operating expenses	267,070	270,620
Operating income	40,072	44,448
Elimination of inter-segment revenues
Segment Reporting Information [Line Items]
Revenues	(85)	(253)
Operating expenses	(85)	(253)
Corporate
Segment Reporting Information [Line Items]
Revenues	0	0
Operating expenses	13,757	13,886
Operating income	(13,757)	(13,886)
Digital Media | Reportable segments
Segment Reporting Information [Line Items]
Revenues	234,211	234,827
Operating expenses	205,742	202,707
Operating income	28,469	32,120
Cybersecurity and Martech | Reportable segments
Segment Reporting Information [Line Items]
Revenues	73,016	80,494
Operating expenses	61,413	68,166
Operating income	$ 11,603	$ 12,328