Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Current assets
Cash and cash equivalents	$ 174,994	$ 55,069
Short-term investments	74,390	93,901
Accounts receivable, net of allowance for doubtful accounts of $317 and $413	59,136	68,782
Deferred costs	13,705	11,898
Prepaid expenses and other current assets	4,824	5,079
Total current assets	327,049	234,729
Long-term assets
Property and equipment, net of accumulated depreciation of $20,982 and $17,091	9,352	10,437
Long-term investments	5,493
Deferred costs, net of current portion	18,155	17,182
Acquisition-related intangible assets, net	19,008
Goodwill	31,004
Other long-term assets	989	983
Total assets	411,050	263,331
Current liabilities
Accounts payable	6,753	5,598
Accrued payroll and other expenses	16,484	16,481
Deferred revenue	118,346	116,831
Deferred rent	940	892
Capital leases	25	21
Total current liabilities	142,548	139,823
Long-term liabilities
Convertible senior notes, net	108,153
Deferred revenue, net of current portion	6,022	2,470
Deferred rent, net of current portion	2,987	3,483
Capital leases, net of current portion	110	26
Asset retirement obligation	198	199
Total liabilities	260,018	146,001
Commitments and contingencies (Note 14)
Stockholders’ equity
Class A and Class B Common stock	5	4
Additional paid-in capital	361,277	314,301
Accumulated other comprehensive income (loss)	11	(110)
Accumulated deficit	(210,261)	(196,865)
Total stockholders’ equity	151,032	117,330
Total liabilities and stockholders' equity	$ 411,050	$ 263,331