Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 51,562	$ 53,148
Short-term investments	39,178	18,779
Accounts receivable, net of allowance for doubtful accounts of $1,478 and $1,061 at December 31, 2017 and 2016, respectively	73,661	49,154
Prepaid expenses and other current assets	8,877	9,152
Total current assets	173,278	130,233
Long-term investments	1,102	20,162
Property and equipment, net	8,589	8,088
Goodwill	83,164	75,110
Intangible assets, net	16,640	8,946
Other assets	1,363	764
Total assets	284,136	243,303
Current liabilities:
Accounts payable	2,240	4,012
Accrued expenses	29,728	23,499
Deferred revenue, current portion	155,811	116,903
Other current liabilities	1,706	1,195
Total current liabilities	189,485	145,609
Deferred revenue, non-current portion	68,689	52,160
Other long-term liabilities	1,809	3,496
Total liabilities	259,983	201,265
Stockholders’ equity:
Preferred stock, $0.01 par value per share; 10,000,000 shares authorized at December 31, 2017 and 2016; 0 shares issued and outstanding at December 31, 2017 and 2016	0	0
Common stock, $0.01 par value per share; 100,000,000 shares authorized at December 31, 2017 and 2016; 44,540,544 and 43,018,737 shares issued at December 31, 2017 and 2016, respectively; 44,053,736 and 42,554,683 shares outstanding at December 31, 2017 and 2016, respectively	441	426
Treasury stock, at cost, 486,808 and 464,054 shares at December 31, 2017 and 2016, respectively	(4,764)	(4,391)
Additional paid-in-capital	463,428	435,360
Accumulated other comprehensive loss	(39)	(19)
Accumulated deficit	(434,913)	(389,338)
Total stockholders’ equity	24,153	42,038
Total liabilities and stockholders’ equity	$ 284,136	$ 243,303