Business Combinations - Schedule of Purchased Intangible Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Business Acquisition [Line Items]
Intangible assets	$ 491,983	$ 454,453
Less: accumulated amortization	(365,916)	(320,033)
Total net intangible assets	126,067	134,420
Developed technology
Business Acquisition [Line Items]
Intangible assets	178,303	148,303
Content
Business Acquisition [Line Items]
Intangible assets	158,700	158,700
Customer relationships
Business Acquisition [Line Items]
Intangible assets	122,450	115,690
Contract backlog
Business Acquisition [Line Items]
Intangible assets	13,200	13,200
Trade names
Business Acquisition [Line Items]
Intangible assets	17,930	17,160
Non-competition agreements
Business Acquisition [Line Items]
Intangible assets	$ 1,400	$ 1,400