Equity Compensation (Tables)

9 Months Ended

Sep. 30, 2018

Equity Compensation

Summary of stock option activity

				Weighted
				Average
	Shares Subject	Weighted		Remaining
	to Options	Average		Contractual
	Outstanding	Exercise Price		Life (Years)
Balance at December 31, 2017	2,069,802		12.13
Exercised	(942,665)		11.38
Expired	(2,809)		5.72
Forfeited	(5,048)		13.42
Balance at September 30, 2018	1,119,280		12.77
Exercisable options at September 30, 2018	1,031,009		12.93	4.7
Vested and expected to vest at September 30, 2018	1,119,280		12.77	4.9

Summary of stock options outstanding and exercisable

The following table summarizes information about stock options outstanding and exercisable at September 30, 2018:

				Options Outstanding				Options Exercisable
							Weighted-		Weighted-
				Weighted			Average		Average
				Average		Number of	Remaining	Number of	Remaining
				Exercise		Underlying	Contractual	Underlying	Contractual
Range of Exercise Prices				Price		Shares	Life (in years)	Shares	Life (in years)
$	4.89	-	7.49		6.12	315,730	2.8	309,965	2.7
$	8.16	-	12.93		10.51	287,084	5.5	228,793	5.3
$	12.98	-	19.56		15.60	284,397	6.1	260,182	6.1
$	20.91	-	22.92		21.15	232,069	5.4	232,069	5.4
						1,119,280		1,031,009

Summary of aggregate intrinsic-value of options exercised, exercisable, and vested and expected to vest

The following table summarizes the aggregate intrinsic-value of options exercised, exercisable and vested and expected to vest (in thousands):

	For the Nine Months Ended
	and as of September 30,
	2018		2017
Options Exercised	$	18,077	$	8,927
Options Exercisable		22,068		39,360
Options Vested and Expected to Vest		24,130		45,152

Summary of restricted stock unit activity

	Number of	Weighted Average
	Shares	Grant Date Fair Value
Non-vested balance at December 31, 2017	1,290,660	$	9.75
Awarded	461,350		28.46
Vested	(743,514)		10.04
Forfeited	(53,880)		11.18
Non-vested balance at September 30, 2018	954,616		18.49

Schedule of total stock-based compensation expense classified in Statements of Operations

Total stock-based compensation expense has been classified as follows in the accompanying Condensed Consolidated Statements of Operations (in thousands):

	Three Months Ended				Nine Months Ended
	September 30,				September 30,
	2018		2017		2018		2017
Cost of revenue	$	59	$	66	$	182	$	185
Research and development		1,115		1,031		3,233		3,210
Sales and marketing		941		883		2,877		2,831
General and administrative		1,314		1,048		3,793		2,965
Total stock-based compensation expense	$	3,429	$	3,028	$	10,085	$	9,191