Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 279,343	$ 123,413
Short-term investments	36,313	116,158
Accounts receivable, net of allowance for doubtful accounts of $2,608 and $1,829 at June 30, 2020 and December 31, 2019, respectively	76,823	87,927
Deferred contract acquisition and fulfillment costs, current portion	18,439	17,047
Prepaid expenses and other current assets	20,708	20,051
Total current assets	431,626	364,596
Long-term investments	5,365	22,887
Property and equipment, net	48,904	50,670
Operating lease right-of-use assets	72,005	60,984
Deferred contract acquisition and fulfillment costs, non-current portion	35,815	34,213
Goodwill	213,686	97,866
Intangible assets, net	47,706	28,561
Other assets	5,304	5,136
Total assets	860,411	664,913
Current liabilities:
Accounts payable	7,078	6,836
Accrued expenses	36,165	41,021
Operating lease liabilities, current portion	9,436	7,179
Deferred revenue, current portion	227,318	231,518
Other current liabilities	0	119
Total current liabilities	279,997	286,673
Convertible senior notes, net	368,161	185,200
Operating lease liabilities, non-current portion	80,081	72,294
Deferred revenue, non-current portion	33,280	36,226
Other long-term liabilities	8,204	1,352
Total liabilities	769,723	581,745
Stockholders’ equity:
Preferred stock, $0.01 par value per share; 10,000,000 shares authorized at June 30, 2020 and December 31, 2019; 0 shares issued at June 30, 2020 and December 31, 2019	0	0
Common stock, $0.01 par value per share; 100,000,000 shares authorized at June 30, 2020 and December 31, 2019; 51,438,042 and 50,397,922 shares issued at June 30, 2020 and December 31, 2019, respectively; 50,951,234 and 49,911,114 shares outstanding at June 30, 2020 and December 31, 2019, respectively	509	499
Treasury stock, at cost, 486,808 shares at June 30, 2020 and December 31, 2019	(4,764)	(4,764)
Additional paid-in-capital	657,678	605,650
Accumulated other comprehensive income	85	213
Accumulated deficit	(562,820)	(518,430)
Total stockholders’ equity	90,688	83,168
Total liabilities and stockholders’ equity	$ 860,411	$ 664,913