Business Combinations - Identifiable Finite-lived Intangible Assets (Details) - USD ($) $ in Thousands	1 Months Ended				12 Months Ended
	Feb. 28, 2019	Sep. 30, 2018	Aug. 31, 2018	Feb. 28, 2017	Dec. 31, 2019	Dec. 31, 2018
Trade names
Acquisitions
Intangible assets, estimated life					5 years
Other Acquisitions
Acquisitions
Intangible assets					$ 22,986
Other Acquisitions | Telecommunication licenses
Acquisitions
Intangible assets					4,370
Other Acquisitions | Developed technology
Acquisitions
Intangible assets					11,771
Other Acquisitions | Customer relationships
Acquisitions
Intangible assets					5,185
Other Acquisitions | Supplier relationships
Acquisitions
Intangible assets					1,660
SendGrid
Acquisitions
Intangible assets					483,000
SendGrid | Developed technology
Acquisitions
Intangible assets					294,000
Intangible assets, estimated life	7 years
SendGrid | Customer relationships
Acquisitions
Intangible assets					169,000
Intangible assets, estimated life	7 years
SendGrid | Trade names
Acquisitions
Intangible assets					$ 20,000
Intangible assets, estimated life	5 years
Ytica
Acquisitions
Intangible assets						$ 9,920
Ytica | Developed technology
Acquisitions
Intangible assets						9,090
Intangible assets, estimated life		4 years
Ytica | Customer relationships
Acquisitions
Intangible assets						$ 830
Intangible assets, estimated life		2 years
Core Network Dynamics Gmbh
Acquisitions
Intangible assets			$ 4,500
Core Network Dynamics Gmbh | Developed technology
Acquisitions
Intangible assets			$ 3,910
Intangible assets, estimated life			4 years
Core Network Dynamics Gmbh | Customer relationships
Acquisitions
Intangible assets			$ 590
Intangible assets, estimated life			6 months
Beepsend
Acquisitions
Intangible assets				$ 13,700
Beepsend | Developed technology
Acquisitions
Intangible assets				$ 5,000
Intangible assets, estimated life				4 years
Beepsend | Customer relationships
Acquisitions
Intangible assets				$ 6,100
Beepsend | Supplier relationships
Acquisitions
Intangible assets				$ 2,600
Intangible assets, estimated life				5 years
Minimum | Developed technology
Acquisitions
Intangible assets, estimated life					3 years
Minimum | Customer relationships
Acquisitions
Intangible assets, estimated life					2 years
Minimum | Supplier relationships
Acquisitions
Intangible assets, estimated life					2 years
Minimum | Other Acquisitions | Developed technology
Acquisitions
Intangible assets, estimated life				4 years
Minimum | Other Acquisitions | Customer relationships
Acquisitions
Intangible assets, estimated life				3 years
Minimum | Other Acquisitions | Supplier relationships
Acquisitions
Intangible assets, estimated life				2 years
Minimum | Beepsend | Customer relationships
Acquisitions
Intangible assets, estimated life				7 years
Maximum | Developed technology
Acquisitions
Intangible assets, estimated life					7 years
Maximum | Customer relationships
Acquisitions
Intangible assets, estimated life					8 years
Maximum | Supplier relationships
Acquisitions
Intangible assets, estimated life					5 years
Maximum | Other Acquisitions | Developed technology
Acquisitions
Intangible assets, estimated life				6 years
Maximum | Other Acquisitions | Customer relationships
Acquisitions
Intangible assets, estimated life				5 years
Maximum | Beepsend | Customer relationships
Acquisitions
Intangible assets, estimated life				8 years