Revenues (Disaggregation of Revenue) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation of Revenue [Line Items]
Total revenues	$ 356,976	$ 344,141	$ 1,020,353	$ 966,466
Point in time
Disaggregation of Revenue [Line Items]
Total revenues	8,396	10,371	19,366	24,315
Over time
Disaggregation of Revenue [Line Items]
Total revenues	348,580	333,770	1,000,987	942,151
Operating Segments
Disaggregation of Revenue [Line Items]
Total revenues	356,976	344,138	1,020,352	966,460
Operating Segments | Digital Media
Disaggregation of Revenue [Line Items]
Total revenues	186,784	172,992	513,462	474,034
Operating Segments | Digital Media | Advertising
Disaggregation of Revenue [Line Items]
Total revenues	135,219	123,463	371,403	339,024
Operating Segments | Digital Media | Subscription
Disaggregation of Revenue [Line Items]
Total revenues	49,386	47,048	136,534	128,402
Operating Segments | Digital Media | Other
Disaggregation of Revenue [Line Items]
Total revenues	2,179	2,481	5,525	6,608
Operating Segments | Cloud Services
Disaggregation of Revenue [Line Items]
Total revenues	170,248	171,163	507,090	492,540
Operating Segments | Cloud Services | Subscription
Disaggregation of Revenue [Line Items]
Total revenues	170,233	170,971	507,021	491,669
Operating Segments | Cloud Services | Other
Disaggregation of Revenue [Line Items]
Total revenues	15	192	69	871
Corporate
Disaggregation of Revenue [Line Items]
Total revenues	0	3	1	6
Elimination of inter-segment
Disaggregation of Revenue [Line Items]
Total revenues	$ (56)	$ (17)	$ (200)	$ (114)