Business Combinations - Additional Information (Details) - USD ($)								3 Months Ended	9 Months Ended	12 Months Ended
	Aug. 04, 2020	May 27, 2020	Mar. 19, 2020	Feb. 25, 2020	Feb. 07, 2020	Jul. 29, 2019	Apr. 01, 2019	Sep. 30, 2020	Sep. 30, 2020	Dec. 31, 2019
Business Acquisition [Line Items]
Contingent consideration								$ 7,996,000	$ 7,996,000
Common stock reserved for future issuance								5,000,000.0	5,000,000.0
Goodwill								$ 183,548,000	$ 183,548,000	$ 91,421,000
Connexient
Business Acquisition [Line Items]
Date of acquisition of business					Feb. 07, 2020
Total purchase price					$ 20,200,000				20,006,000
Cash paid					$ 11,500,000				10,991,000
Number of newly issued common stock					96,611
Common stock price per share					$ 93.32
Contingent payment					$ 6,000,000.0
Contingent consideration								0	$ 0
Weighted average useful life of identified acquired intangible assets									7 years 11 months 1 day
Goodwill					$ 14,343,000
Connexient | General and Administrative Expenses
Business Acquisition [Line Items]
Business acquisition transaction costs									$ 100,000
Connexient | Acquired Technology
Business Acquisition [Line Items]
Weighted average useful life of identified acquired intangible assets									3 years
Connexient | Customer Relationships
Business Acquisition [Line Items]
Weighted average useful life of identified acquired intangible assets									9 years
Connexient | Trade Names
Business Acquisition [Line Items]
Weighted average useful life of identified acquired intangible assets									4 years
CNL Software Limited
Business Acquisition [Line Items]
Date of acquisition of business				Feb. 25, 2020
Total purchase price				$ 35,700,000					$ 33,980,000
Cash paid				$ 19,800,000					$ 18,030,000
Number of newly issued common stock				153,217
Common stock price per share				$ 104.10
Weighted average useful life of identified acquired intangible assets									5 years 3 days
Increase in deferred revenue and goodwill								2,600,000
Goodwill				$ 30,734,000
CNL Software Limited | General and Administrative Expenses
Business Acquisition [Line Items]
Business acquisition transaction costs									$ 100,000
CNL Software Limited | Acquired Technology
Business Acquisition [Line Items]
Weighted average useful life of identified acquired intangible assets									3 years
CNL Software Limited | Customer Relationships
Business Acquisition [Line Items]
Weighted average useful life of identified acquired intangible assets									6 years
CNL Software Limited | Trade Names
Business Acquisition [Line Items]
Weighted average useful life of identified acquired intangible assets									4 years
One2Many Group B.V.
Business Acquisition [Line Items]
Date of acquisition of business			Mar. 19, 2020
Total purchase price			$ 13,100,000						$ 14,222,000
Cash paid			$ 5,500,000						6,563,000
Number of newly issued common stock			52,113
Common stock price per share			$ 104.95
Contingent payment			$ 15,000,000.0
Contingent consideration			2,190,000					1,400,000	$ 1,400,000
Weighted average useful life of identified acquired intangible assets									5 years 8 months 1 day
Business acquisition transaction costs									$ 100,000
Purchase liabilities			2,000,000.0
Goodwill			$ 10,704,000
One2Many Group B.V. | Acquired Technology
Business Acquisition [Line Items]
Weighted average useful life of identified acquired intangible assets									3 years
One2Many Group B.V. | Customer Relationships
Business Acquisition [Line Items]
Weighted average useful life of identified acquired intangible assets									7 years
One2Many Group B.V. | Trade Names
Business Acquisition [Line Items]
Weighted average useful life of identified acquired intangible assets									3 years
Techwan SA
Business Acquisition [Line Items]
Date of acquisition of business		May 27, 2020
Total purchase price		$ 15,500,000							$ 17,300,000
Cash paid		$ 9,400,000							9,301,000
Number of newly issued common stock		38,425
Common stock price per share		$ 132.05
Contingent payment		$ 7,000,000.0
Contingent consideration		2,030,000						100,000	$ 100,000
Weighted average useful life of identified acquired intangible assets									7 years 5 months 19 days
Purchase liabilities		$ 100,000
Common stock reserved for future issuance		6,779
Goodwill		$ 12,797,000
Techwan SA | General and Administrative Expenses
Business Acquisition [Line Items]
Business acquisition transaction costs									$ 200,000
Techwan SA | Acquired Technology
Business Acquisition [Line Items]
Weighted average useful life of identified acquired intangible assets									3 years
Techwan SA | Customer Relationships
Business Acquisition [Line Items]
Weighted average useful life of identified acquired intangible assets									9 years
Techwan SA | Trade Names
Business Acquisition [Line Items]
Weighted average useful life of identified acquired intangible assets									3 years
SnapComms Limited
Business Acquisition [Line Items]
Date of acquisition of business	Aug. 04, 2020
Total purchase price	$ 34,200,000								$ 32,739,000
Cash paid	$ 13,200,000								$ 9,858,000
Number of newly issued common stock	121,858
Common stock price per share	$ 145.13
Contingent payment	$ 5,000,000.0
Contingent consideration	2,047,000
Weighted average useful life of identified acquired intangible assets									7 years 9 months 29 days
Contingent consideration expect to pay	3,300,000
Goodwill	$ 23,455,000
SnapComms Limited | General and Administrative Expenses
Business Acquisition [Line Items]
Business acquisition transaction costs									$ 100,000
SnapComms Limited | Acquired Technology
Business Acquisition [Line Items]
Weighted average useful life of identified acquired intangible assets									3 years
SnapComms Limited | Customer Relationships
Business Acquisition [Line Items]
Weighted average useful life of identified acquired intangible assets									9 years
SnapComms Limited | Trade Names
Business Acquisition [Line Items]
Weighted average useful life of identified acquired intangible assets									3 years
Mission Mode
Business Acquisition [Line Items]
Date of acquisition of business							Apr. 01, 2019
Total purchase price							$ 6,800,000
Contingent payment							1,000,000.0
Contingent consideration							$ 600,000
NC4 Inc., NC4 Public Sector LLC, and Celerium Group
Business Acquisition [Line Items]
Date of acquisition of business						Jul. 29, 2019
NC4 Inc. and NC4 Public Sector LLC
Business Acquisition [Line Items]
Total purchase price						$ 84,500,000				84,453,000
Cash paid						$ 51,700,000
Number of newly issued common stock						320,998
Common stock price per share						$ 102.18
Weighted average useful life of identified acquired intangible assets									5 years 10 months 17 days
Business acquisition transaction costs									$ 200,000
Goodwill								$ 40,400,000	$ 40,400,000	$ 40,384,000
NC4 Inc. and NC4 Public Sector LLC | Acquired Technology
Business Acquisition [Line Items]
Weighted average useful life of identified acquired intangible assets									3 years
NC4 Inc. and NC4 Public Sector LLC | Customer Relationships
Business Acquisition [Line Items]
Weighted average useful life of identified acquired intangible assets									7 years
NC4 Inc. and NC4 Public Sector LLC | Trade Names
Business Acquisition [Line Items]
Weighted average useful life of identified acquired intangible assets									3 years