Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 53,068	$ 53,148
Short-term investments	31,213	18,779
Accounts receivable, net of allowance for doubtful accounts of $1,240 and $1,061 at June 30, 2017 and December 31, 2016, respectively	47,560	49,154
Prepaid expenses and other current assets	8,892	9,152
Total current assets	140,733	130,233
Long-term investments	8,799	20,162
Property and equipment, net	8,287	8,088
Goodwill	75,110	75,110
Intangible assets, net	8,294	8,946
Other assets	630	764
Total assets	241,853	243,303
Current liabilities:
Accounts payable	2,257	4,012
Accrued expenses	20,667	23,499
Deferred revenue, current portion	126,085	116,903
Other current liabilities	1,334	1,195
Total current liabilities	150,343	145,609
Deferred revenue, non-current portion	54,344	52,160
Other long-term liabilities	2,539	3,496
Total liabilities	207,226	201,265
Stockholders’ equity:
Preferred stock, $0.01 par value per share; 10,000,000 shares authorized at June 30, 2017 and December 31, 2016; 0 shares issued at June 30, 2017 and December 31, 2016	0	0
Common stock, $0.01 par value per share; 100,000,000 shares authorized at June 30, 2017 and December 31, 2016; 44,005,649 and 43,018,737 shares issued at June 30, 2017 and December 31, 2016, respectively; 43,532,061 and 42,554,683 shares outstanding at June 30, 2017 and December 31, 2016, respectively	435	426
Treasury stock, at cost, 473,588 and 464,054 shares at June 30, 2017 and December 31, 2016, respectively	(4,531)	(4,391)
Additional paid-in-capital	450,394	435,360
Accumulated other comprehensive loss	(46)	(19)
Accumulated deficit	(411,625)	(389,338)
Total stockholders’ equity	34,627	42,038
Total liabilities and stockholders’ equity	$ 241,853	$ 243,303