Summary of Significant Accounting Policies - Additional Information (Details)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020 USD ($) Customer	Sep. 30, 2019 Customer	Sep. 30, 2020 USD ($) Customer	Sep. 30, 2019 Customer	Dec. 31, 2019 Customer
Impairment charges | $			$ 0
Subscription contracts			The Company’s subscription contracts are generally two years or longer in length, billed annually in advance, and non-cancelable.
Deferred sales commission cost amortization period			4 years
ASU 2016-13
Change in Accounting Principle, Accounting Standards Update, Adopted [true false]	true		true
Change in Accounting Principle, Accounting Standards Update, Adoption Date	Jan. 01, 2020		Jan. 01, 2020
Change in Accounting Principle, Accounting Standards Update, Immaterial Effect [true false]	true		true
Change in Accounting Principle, Accounting Standards Update, Transition Option Elected [Extensible List]			evbg:AccountingStandardsUpdate201613RetrospectiveMember
ASU 2018-13
Change in Accounting Principle, Accounting Standards Update, Adopted [true false]	true		true
Change in Accounting Principle, Accounting Standards Update, Adoption Date	Jan. 01, 2020		Jan. 01, 2020
Change in Accounting Principle, Accounting Standards Update, Immaterial Effect [true false]	true		true
Change in Accounting Principle, Accounting Standards Update, Transition Option Elected [Extensible List]			evbg:AccountingStandardsUpdate201813ProspectiveMember
ASU 2018-15
Change in Accounting Principle, Accounting Standards Update, Adopted [true false]	true		true
Change in Accounting Principle, Accounting Standards Update, Adoption Date	Jan. 01, 2020		Jan. 01, 2020
Change in Accounting Principle, Accounting Standards Update, Immaterial Effect [true false]	true		true
Change in Accounting Principle, Accounting Standards Update, Transition Option Elected [Extensible List]			us-gaap:AccountingStandardsUpdate201815ProspectiveMember
Customer Concentration Risk | Revenue
Number of customers above 10% threshold | Customer	0	0	0	0
Customer Concentration Risk | Accounts Receivable
Number of customers above 10% threshold | Customer			0		0
Maximum
Cash and cash equivalent, FDIC insured amount | $	$ 250,000		$ 250,000