Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 239,409	$ 123,413
Short-term investments	81,209	116,158
Accounts receivable, net of allowance for doubtful accounts of $3,203 and $1,829 at September 30, 2020 and December 31, 2019, respectively	73,625	87,927
Deferred contract acquisition and fulfillment costs, current portion	19,269	17,047
Prepaid expenses and other current assets	20,521	20,051
Total current assets	434,033	364,596
Long-term investments	10,813	22,887
Property and equipment, net	50,305	50,670
Operating lease right-of-use assets	69,797	60,984
Deferred contract acquisition and fulfillment costs, non-current portion	37,269	34,213
Goodwill	213,727	97,866
Intangible assets, net	45,942	28,561
Other assets	4,931	5,136
Total assets	866,817	664,913
Current liabilities:
Accounts payable	9,033	6,836
Accrued expenses	48,035	41,021
Operating lease liabilities, current portion	9,568	7,179
Deferred revenue, current portion	231,560	231,518
Other current liabilities	85	119
Total current liabilities	298,281	286,673
Convertible senior notes, net	373,318	185,200
Operating lease liabilities, non-current portion	77,863	72,294
Deferred revenue, non-current portion	30,632	36,226
Other long-term liabilities	1,370	1,352
Total liabilities	781,464	581,745
Stockholders’ equity:
Preferred stock, $0.01 par value per share; 10,000,000 shares authorized at September 30, 2020 and December 31, 2019; 0 shares issued at September 30, 2020 and December 31, 2019	0	0
Common stock, $0.01 par value per share; 100,000,000 shares authorized at September 30, 2020 and December 31, 2019; 52,264,083 and 50,397,922 shares issued at September 30, 2020 and December 31, 2019, respectively; 51,777,275 and 49,911,114 shares outstanding at September 30, 2020 and December 31, 2019, respectively	518	499
Treasury stock, at cost, 486,808 shares at September 30, 2020 and December 31, 2019	(4,764)	(4,764)
Additional paid-in-capital	677,983	605,650
Accumulated other comprehensive (loss) income	(23)	213
Accumulated deficit	(588,361)	(518,430)
Total stockholders’ equity	85,353	83,168
Total liabilities and stockholders’ equity	$ 866,817	$ 664,913

Carrying value as of the balance sheet date of liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received that are used in an entity's business. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

Name:	us-gaap_AccountsPayableCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount, after allowance for credit loss, of right to consideration from customer for product sold and service rendered in normal course of business.