Segment Information (Reconciliation of Total Segment Operating Income to Consolidated Operating Income) (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Segment Reporting Information [Line Items]
Revenues	$ 337,356	$ 341,293	$ 652,424	$ 652,950
Gross profit	291,352	292,508	560,320	560,313
Direct costs	245,456	282,453	483,871	523,377
Income from operations	45,887	10,055	76,449	36,936
Reportable segments
Segment Reporting Information [Line Items]
Revenues	337,356	341,293	652,424	652,950
Gross profit	291,352	292,517	560,320	560,387
Direct costs	234,152	269,606	458,672	494,958
Income from operations	57,200	22,911	101,648	65,429
Elimination of inter-segment revenues
Segment Reporting Information [Line Items]
Revenues	(254)	(292)	(507)	(410)
Gross profit	(358)	(76)	(489)	(126)
Direct costs	(358)	(76)	(489)	(126)
Corporate
Segment Reporting Information [Line Items]
Revenues	0	0	0	0
Gross profit	0	(9)	0	(74)
Direct costs	11,304	12,847	25,199	28,419
Income from operations	(11,313)	(12,856)	(25,199)	(28,493)
Digital Media \| Reportable segments
Segment Reporting Information [Line Items]
Revenues	258,700	253,977	493,527	480,850
Gross profit	233,447	228,698	443,153	434,759
Direct costs	188,824	184,592	366,410	360,010
Income from operations	44,623	44,106	76,743	74,749
Cybersecurity and Martech \| Reportable segments
Segment Reporting Information [Line Items]
Revenues	78,910	87,608	159,404	172,510
Gross profit	58,263	63,895	117,656	125,754
Direct costs	45,686	85,090	92,751	135,074
Income from operations	$ 12,577	$ (21,195)	$ 24,905	$ (9,320)