CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 54,043	$ 47,234
Short-term investments	36,184	49,576
Accounts receivable, net of allowance for doubtful accounts of $433 and $628 at December 31, 2016 and December 31, 2015, respectively	43,755	42,674
Prepaid expenses and other current assets	6,131	4,809
TOTAL CURRENT ASSETS	140,113	144,293
Long-term investments		2,094
Property and equipment-net	5,503	6,572
Intangible assets-net	645	1,261
Goodwill	5,475	5,475
Other assets	1,370	1,419
TOTAL ASSETS	153,106	161,114
Current liabilities:
Accounts payable	701	2,551
Accrued expenses	21,674	19,196
Deferred revenue-current	68,153	55,978
TOTAL CURRENT LIABILITIES	90,528	77,725
Long-term liabilities:
Deferred revenue-noncurrent	19,923	13,897
Other long-term liabilities	1,838	1,353
TOTAL LIABILITIES	112,289	92,975
Commitments and contingencies (Note 13)
Stockholders' equity:
Common stock, $0.0001 par value, 300,000,000 shares authorized, 89,066,031 shares and 81,326,237 shares issued and outstanding at December 31, 2016 and December 31, 2015, respectively	9	8
Additional paid-in capital	383,193	343,336
Accumulated deficit	(342,385)	(275,205)
TOTAL STOCKHOLDERS' EQUITY	40,817	68,139
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$ 153,106	$ 161,114