Business Combinations - Additional Information (Details) - USD ($)						12 Months Ended
	Jul. 29, 2019	Apr. 01, 2019	May 18, 2018	May 01, 2018	Apr. 03, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Business Acquisition [Line Items]
Decrease in contingent consideration obligation						$ 550,000	$ 250,000	$ 1,020,000
Goodwill						91,421,000	48,382,000	31,328,000
Purchase price of acquisition, cash						$ 58,419,000	35,857,000	$ 21,235,000
Maximum
Business Acquisition [Line Items]
Estimated useful life						7 years
Maximum | Customer Relationships
Business Acquisition [Line Items]
Weighted average useful life of identified acquired intangible assets						7 years
Maximum | Trade Names
Business Acquisition [Line Items]
Weighted average useful life of identified acquired intangible assets						7 years
Minimum
Business Acquisition [Line Items]
Estimated useful life						1 year
Minimum | Customer Relationships
Business Acquisition [Line Items]
Weighted average useful life of identified acquired intangible assets						5 years
Minimum | Trade Names
Business Acquisition [Line Items]
Weighted average useful life of identified acquired intangible assets						1 year
MissionMode Solutions, Inc.
Business Acquisition [Line Items]
Date of acquisition of business		Apr. 01, 2019
Total purchase price		$ 6,800,000				$ 7,314,000
Note payable		600,000				$ 550,000
Weighted average useful life of identified acquired intangible assets						6 years 6 months
Goodwill		2,900,000				$ 2,918,000
Cash paid						$ 6,764,000
MissionMode Solutions, Inc. | Acquired Technology
Business Acquisition [Line Items]
Weighted average useful life of identified acquired intangible assets						3 years
MissionMode Solutions, Inc. | Customer Relationships
Business Acquisition [Line Items]
Weighted average useful life of identified acquired intangible assets						7 years
MissionMode Solutions, Inc. | Trade Names
Business Acquisition [Line Items]
Weighted average useful life of identified acquired intangible assets						1 year
MissionMode Solutions, Inc. | General and Administrative Expenses
Business Acquisition [Line Items]
Decrease in contingent consideration obligation						$ 600,000
Business acquisition transaction costs						$ 100,000
MissionMode Solutions, Inc. | Maximum
Business Acquisition [Line Items]
Contingent payment		$ 1,000,000.0
Estimated useful life						7 years
MissionMode Solutions, Inc. | Minimum
Business Acquisition [Line Items]
Estimated useful life						1 year
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
Weighted average useful life of identified acquired intangible assets						5 years 10 months 17 days
Goodwill	40,400,000					$ 40,384,000
Cash paid	$ 51,700,000
Number of newly issued common stock	320,998
Common stock price per share	$ 102.18
Purchase price of acquisition, cash						$ 51,655,000
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
NC4 Inc. and NC4 Public Sector LLC | General and Administrative Expenses
Business Acquisition [Line Items]
Business acquisition transaction costs						$ 200,000
NC4 Inc. and NC4 Public Sector LLC | Maximum
Business Acquisition [Line Items]
Estimated useful life						7 years
NC4 Inc. and NC4 Public Sector LLC | Minimum
Business Acquisition [Line Items]
Estimated useful life						3 years
UMS
Business Acquisition [Line Items]
Date of acquisition of business					Apr. 03, 2018
Total purchase price					$ 31,884,000
Weighted average useful life of identified acquired intangible assets						6 years 7 months 17 days
Goodwill					18,278,000
Cash paid					31,884,000
Purchase price of acquisition, cash					$ 31,900,000
UMS | Acquired Technology
Business Acquisition [Line Items]
Weighted average useful life of identified acquired intangible assets						3 years
UMS | Customer Relationships
Business Acquisition [Line Items]
Weighted average useful life of identified acquired intangible assets						7 years
UMS | Trade Names
Business Acquisition [Line Items]
Weighted average useful life of identified acquired intangible assets						1 year
UMS | General and Administrative Expenses
Business Acquisition [Line Items]
Business acquisition transaction costs							400,000
PlanetRisk, Inc.
Business Acquisition [Line Items]
Date of acquisition of business				May 01, 2018
Total purchase price				$ 2,021,000
Weighted average useful life of identified acquired intangible assets						6 years 9 months 27 days
Goodwill				228,000
Cash paid				2,021,000
Purchase price of acquisition, cash				$ 2,000,000.0
PlanetRisk, Inc. | Acquired Technology
Business Acquisition [Line Items]
Weighted average useful life of identified acquired intangible assets						3 years
PlanetRisk, Inc. | Customer Relationships
Business Acquisition [Line Items]
Weighted average useful life of identified acquired intangible assets						7 years
PlanetRisk, Inc. | General and Administrative Expenses
Business Acquisition [Line Items]
Business acquisition transaction costs							100,000
Respond B.V.
Business Acquisition [Line Items]
Date of acquisition of business			May 18, 2018
Total purchase price			$ 2,335,000
Note payable			400,000
Weighted average useful life of identified acquired intangible assets						6 years 4 months 24 days
Goodwill			1,193,000
Cash paid			1,952,000
Purchase price of acquisition, cash			$ 2,000,000.0
Respond B.V. | Acquired Technology
Business Acquisition [Line Items]
Weighted average useful life of identified acquired intangible assets						3 years
Respond B.V. | Customer Relationships
Business Acquisition [Line Items]
Weighted average useful life of identified acquired intangible assets						7 years
Respond B.V. | Trade Names
Business Acquisition [Line Items]
Weighted average useful life of identified acquired intangible assets						1 year
Respond B.V. | General and Administrative Expenses
Business Acquisition [Line Items]
Business acquisition transaction costs							$ 100,000