Acquisitions - Intangible Assets Acquired (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($)
Sapho, Inc.
Acquired Finite-Lived Intangible Assets [Line Items]
Identifiable intangible assets acquired	$ 53,600
Weighted average useful life	5 years
Sapho, Inc. | Customer Contracts
Acquired Finite-Lived Intangible Assets [Line Items]
Identifiable intangible assets acquired	$ 1,600
Weighted average useful life	5 years
Sapho, Inc. | Developed Technology
Acquired Finite-Lived Intangible Assets [Line Items]
Identifiable intangible assets acquired	$ 52,000
Weighted average useful life	5 years
Sapho, Inc. | Tradenames
Acquired Finite-Lived Intangible Assets [Line Items]
Identifiable intangible assets acquired	$ 0
Cedexis, Inc.
Acquired Finite-Lived Intangible Assets [Line Items]
Identifiable intangible assets acquired	27,200
Cedexis, Inc. | Customer Contracts
Acquired Finite-Lived Intangible Assets [Line Items]
Identifiable intangible assets acquired	$ 2,000
Weighted average useful life	1 year
Cedexis, Inc. | Developed Technology
Acquired Finite-Lived Intangible Assets [Line Items]
Identifiable intangible assets acquired	$ 23,800
Cedexis, Inc. | Tradenames
Acquired Finite-Lived Intangible Assets [Line Items]
Identifiable intangible assets acquired	$ 1,400
Weighted average useful life	1 year
Minimum | Cedexis, Inc.
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted average useful life	1 year
Minimum | Cedexis, Inc. | Developed Technology
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted average useful life	5 years
Maximum | Cedexis, Inc.
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted average useful life	6 years
Maximum | Cedexis, Inc. | Developed Technology
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted average useful life	6 years