Stock Incentive Plans (Tables)

12 Months Ended

Dec. 31, 2019

Share-based Payment Arrangement [Abstract]

Summary of Share-based Awards Available for Grant under 2016 Plan

A summary of share-based awards available for grant under the 2016 Equity Incentive Plan is as follows: 

	Shares Available for Grant
Balance at December 31, 2016	3,743,037
Additional options authorized	1,106,966
Awards granted	(837,436)
Awards forfeited	21,585
Balance at December 31, 2017	4,034,152
Additional awards authorized	1,168,865
Awards granted	(666,913)
Awards forfeited	124,478
Awards withheld for tax purposes	56,710
Balance at December 31, 2018	4,717,292
Additional awards authorized	1,218,402
Awards granted	(649,911)
Awards forfeited	181,513
Awards withheld for tax purposes	60,836
Balance at December 31, 2019	5,528,132

Summary of Stock Option Activity Under 2006 and 2016 Plans, Including Grants To Nonemployees

The following table summarizes stock option activity under the 2006 and 2016 Plans, including grants to nonemployees:

		Options Outstanding
	Options Outstanding	Weighted- Average Exercise Price Per Share		Weighted- Average Remaining Contractual Life (years)	Aggregate Intrinsic Value (in thousands)
Balance at December 31, 2016	2,977,218	$	6.16	6.93	$	70,979
Options granted	465,271	$	36.76
Options exercised	(827,556)	$	4.11
Options forfeited	(13,752)	$	14.43
Balance at December 31, 2017	2,601,181	$	12.24	7.17	$	113,958
Options granted	366,928	$	68.32
Options exercised	(798,424)	$	7.19
Options forfeited	(75,548)	$	34.30
Balance at December 31, 2018	2,094,137	$	23.20	7.02	97,976
Options granted	20,010	$	82.77
Options exercised	(540,307)	$	9.59
Options forfeited	(70,593)	$	54.54
Balance at December 31, 2019	1,503,247	$	27.40	6.43	62,401
Options exercisable – December 31, 2019	1,147,525	$	19.64	6.02	55,919
Options vested and expected to vest – December 31, 2019	1,487,867	$	27.07	6.41	62,220

Summary of Non-vested Restricted Stock Units ("RSUs")

The fair value of non-vested restricted stock units (“RSUs”) is based on the Company’s closing stock price on the date of grant. A summary for the year ended December 31, 2019, is as follows:

	Shares Underlying RSUs	Weighted Average Grant Date Fair Value		Weighted Remaining Vesting Period (in years)	Aggregate Intrinsic Value (in thousands)
Non-vested as of December 31, 2018	547,891	$	56.62	2.45	$	38,067
Granted	629,901	$	87.72
Vested	(180,842)	$	52.52
Forfeited	(110,920)	$	69.77
Non-vested as of December 31, 2019	886,030	$	77.92	1.39	$	60,330