CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 99,565	$ 51,562
Short-term investments	159,210	39,178
Accounts receivable, net of allowance for doubtful accounts of $1,624 and $1,478 at December 31, 2018 and 2017, respectively	74,935	73,661
Deferred contract acquisition and fulfillment costs, current portion	12,321	0
Prepaid expenses and other current assets	9,746	8,877
Total current assets	355,777	173,278
Long-term investments	44,892	1,102
Property and equipment, net	17,523	8,589
Goodwill	88,420	83,164
Intangible assets, net	23,955	16,640
Deferred contract acquisition and fulfillment costs, non-current portion	27,634	0
Other assets	1,168	1,363
Total assets	559,369	284,136
Current liabilities:
Accounts payable	7,048	2,240
Accrued expenses	37,376	29,728
Deferred revenue, current portion	189,855	155,811
Other current liabilities	707	1,706
Total current liabilities	234,986	189,485
Convertible senior notes, net	174,688	0
Deferred revenue, non-current portion	58,716	68,689
Other long-term liabilities	3,660	1,809
Total liabilities	472,050	259,983
Stockholders’ equity:
Preferred stock, $0.01 par value per share; 10,000,000 shares authorized at December 31, 2018 and 2017; 0 shares issued and outstanding at December 31, 2018 and 2017	0	0
Common stock, $0.01 par value per share; 100,000,000 shares authorized at December 31, 2018 and 2017; 48,087,257 and 44,540,544 shares issued at December 31, 2018 and 2017, respectively; 47,600,449 and 44,053,736 shares outstanding at December 31, 2018 and 2017, respectively	476	441
Treasury stock, at cost, 486,808 shares at December 31, 2018 and 2017	(4,764)	(4,764)
Additional paid-in-capital	556,223	463,428
Accumulated other comprehensive loss	(31)	(39)
Accumulated deficit	(464,585)	(434,913)
Total stockholders’ equity	87,319	24,153
Total liabilities and stockholders’ equity	$ 559,369	$ 284,136