Goodwill and Intangible Assets - Goodwill and Accumulated Impairment Charges (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Goodwill [Line Items]
Gross Carrying Amount	$ 1,564,084	$ 1,525,000
Accumulated Impairment Charges	32,629	0
Net Book Value	1,531,455	1,525,000	$ 1,313,101
Cybersecurity and Martech
Goodwill [Line Items]
Gross Carrying Amount	567,425	582,066
Accumulated Impairment Charges	32,629	0
Net Book Value	534,796	582,066
Digital Media
Goodwill [Line Items]
Gross Carrying Amount	996,659	942,934
Accumulated Impairment Charges	0	0
Net Book Value	$ 996,659	$ 942,934