Summary of Significant Accounting Policies (Tables)

3 Months Ended

Mar. 31, 2021

Schedule of Revenue Disaggregated by Revenue Type, Geographic Region and Customer

The nature, amount, timing, and uncertainty of our revenue and how revenue and cash flows are affected by economic factors is most appropriately depicted by revenue type, geographic region, and customer vertical.

Revenue by type for the first quarters of 2021 and 2020 was as follows (in thousands):

	Quarter Ended
	March 31,
	2021		2020
Cloud and related solutions	$	227,019	$	222,220
Software and services		14,779		13,206
Maintenance		11,321		10,191
Total revenue	$	253,119	$	245,617

We use the location of the customer as the basis of attributing revenue to geographic regions. Revenue by geographic region for the first quarters of 2021 and 2020, as a percentage of our total revenue, was as follows:

	Quarter Ended
	March 31,
	2021			2020
Americas (principally the U.S.)		86	%		88	%
Europe, Middle East, and Africa		10	%		9	%
Asia Pacific		4	%		3	%
Total revenue		100	%		100	%

We generate our revenue primarily from the global communications markets; however, we serve an expanding group of customers in markets including financial services, healthcare, media and entertainment companies, and government entities. Revenue by customer vertical for the first quarters of 2021 and 2020, as a percentage of our total revenue, was as follows:

	Quarter Ended
	March 31,
	2021			2020
Broadband/Cable/Satellite		57	%		58	%
Telecommunications		18	%		17	%
Other		25	%		25	%
Total revenue		100	%		100	%

Fair Value Measurements

The following table represents the fair value hierarchy based upon three levels of inputs, of which Levels 1 and 2 are considered observable and Level 3 is unobservable, for our financial assets measured at fair value (in thousands):

	March 31, 2021						December 31, 2020
	Level 1		Level 2		Total		Level 1		Level 2		Total
Cash equivalents:
Money market funds	$	33,546	$	—	$	33,546	$	33,535	$	—	$	33,535
Commercial paper		—		9,224		9,224		—		15,746		15,746
Corporate debt securities		—		—		—		—		1,351		1,351
Short-term investments:
Corporate debt securities		—		42,544		42,544		—		38,672		38,672
U.S. government agency bonds		—		4,628		4,628		—		4,642		4,642
Asset-backed securities		—		7,367		7,367		—		8,284		8,284
Total	$	33,546	$	63,763	$	97,309	$	33,535	$	68,695	$	102,230

Carrying Value (Par Value for Convertible Debt) and Estimated Fair Value of Debt

We have chosen not to record our debt at fair value, with changes recognized in earnings each reporting period. The following table indicates the carrying value (par value for convertible debt) and estimated fair value of our debt as of the indicated periods (in thousands):

	March 31, 2021				December 31, 2020
	Carrying		Fair		Carrying		Fair
	Value		Value		Value		Value
2018 Credit Agreement (carrying value including current maturities)	$	123,750	$	123,750	$	126,563	$	126,563
2016 Convertible debt (par value)		230,000		243,513		230,000		244,663