Segment Information (Reconciliation of Total Segment Operating Income to Consolidated Operating Income) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Segment Reporting Information [Line Items]
Revenues	$ 341,873	$ 355,144	$ 994,297	$ 1,008,094
Gross profit	289,270	305,446	849,590	865,759
Operating expenses	260,236	260,436	744,107	783,813
Operating income	29,034	45,010	105,483	81,946
Reportable segments
Segment Reporting Information [Line Items]
Revenues	341,873	355,144	994,297	1,008,094
Gross profit	289,270	305,446	849,590	865,833
Operating expenses	248,123	245,070	706,795	740,028
Operating income	41,147	60,376	142,795	125,805
Elimination of inter-segment revenues
Segment Reporting Information [Line Items]
Revenues	(215)	(356)	(722)	(766)
Gross profit	(212)	(88)	(701)	(214)
Operating expenses	(212)	(88)	(701)	(214)
Corporate
Segment Reporting Information [Line Items]
Revenues	0	0	0	0
Gross profit	0	0	0	(74)
Operating expenses	12,113	15,366	37,312	43,785
Operating income	(12,113)	(15,366)	(37,312)	(43,859)
Digital Media | Reportable segments
Segment Reporting Information [Line Items]
Revenues	263,896	262,429	757,423	743,280
Gross profit	232,887	238,650	676,040	673,409
Operating expenses	205,570	188,950	571,980	548,960
Operating income	27,317	49,700	104,060	124,449
Cybersecurity and Martech | Reportable segments
Segment Reporting Information [Line Items]
Revenues	78,192	93,071	237,596	265,580
Gross profit	56,595	66,884	174,251	192,638
Operating expenses	42,765	56,208	135,516	191,282
Operating income	$ 13,830	$ 10,676	$ 38,735	$ 1,356