Summary of Significant Accounting Policies (Tables)

3 Months Ended

Mar. 31, 2020

Summary of Significant Accounting Policies

Contract assets and contract liabilities

The following table presents changes in the Company’s contract assets and contract liabilities during the three months ended March 31, 2020 and 2019 (in thousands):

	Balance at								Balance at
Three months ended March 31, 2020	December 31, 2019		Additions		Deductions		Impact of Netting		March 31, 2020
Contract asset	$	3,631	$	—	$	(3,000)	$	359	$	990
Contract liabilities	$	127,432	$	—	$	(283)	$	361	$	127,510

	Balance at						Balance at
Three months ended March 31, 2019	December 31, 2018		Additions		Deductions		March 31, 2019
Contract asset	$	500	$	—	$	(500)	$	—
Contract liabilities	$	80,802	$	65,287	$	(79)	$	146,010

The Company recognized the following revenues as a result of changes in contract asset and contract liability balances in the respective periods (in thousands):

	Three Months Ended
	March 31,
	2020		2019
Revenue recognized in the period from:
Amounts included in contract liabilities at the beginning of the period	$	283	$	79
Performance obligations satisfied in previous periods	$	—	$	—

Schedule of assets that are required to be measured at fair value on a recurring basis

As of March 31, 2020, the Company held certain assets that are required to be measured at fair value on a recurring basis. The following table represents the fair value hierarchy for the Company’s financial assets measured at fair value on a recurring basis as of March 31, 2020 (in thousands):

	Fair Value Measurements at March 31, 2020 Using
			Quoted Prices in				Significant
			Active Markets for		Significant Other		Unobservable
			Identical Assets		Observable Inputs		Inputs
	Total		(Level 1)		(Level 2)		(Level 3)
Cash equivalents	$	231,280	$	231,280	$	—	$	—

As of December 31, 2019, the Company held certain assets that are required to be measured at fair value on a recurring basis. The following table represents the fair value hierarchy for the Company’s financial assets measured at fair value on a recurring basis as of December 31, 2019 (in thousands):

	Fair Value Measurements at December 31, 2019 Using
			Quoted Prices in				Significant
			Active Markets for		Significant Other		Unobservable
			Identical Assets		Observable Inputs		Inputs
	Total		(Level 1)		(Level 2)		(Level 3)
Cash equivalents	$	163,674	$	163,674	$	—	$	—

Schedule of common stock equivalents, as calculated in accordance with the treasury-stock method

The Company’s common stock equivalents, as calculated in accordance with the treasury-stock method for the options and unvested restricted stock and the if-converted method for the Convertible Notes, are shown in the following table (in thousands):

	Three Months Ended
	March 31,
	2020	2019
Options outstanding to purchase common stock, shares issuable under the employee stock purchase plan, and unvested restricted stock/units at end of period	19,021	21,528
Common stock equivalents under treasury stock method for options, shares issuable under the employee stock purchase plan, and unvested restricted stock	1,428	1,559
Shares issuable upon conversion of convertible notes at end of period	501	501
Common stock equivalents under if-converted method for convertible notes	501	501

Schedule of assumptions

	Three Months Ended March 31,
	2020	2019
Dividend	None	None
Volatility	84.20%	73.57%
Risk-free interest rate	1.45%	2.47%
Expected life (years)	6.0	6.0

Summary of stock option activity

A summary of option activity under the Company’s equity plans as of March 31, 2020, and changes during the three month period then ended is presented below (in thousands, except weighted-average data):

		Weighted-
	Number	Average
	of Stock	Exercise
	Options	Price
Outstanding at December 31, 2019	13,518	$	7.53
Granted	5,740		4.55
Exercised	(86)		2.81
Forfeited/Canceled	(625)		8.45
Outstanding at March 31, 2020	18,547	$	6.60

Summary of restricted stock activity

A summary of restricted stock and restricted stock unit activity, inclusive of performance-based restricted stock awards, under the Company’s equity plans as of March 31, 2020 and changes during the three-month period ended March 31, 2020 is presented below (in thousands):

	Number of	Weighted-
	Restricted	Average Grant
	Stock Shares	Date Fair Value
Unvested at December 31, 2019	1,297	$	2.97
Vested	(337)		2.47
Forfeited	(487)		3.62
Unvested at March 31, 2020	473		2.68