Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Current assets
Cash and cash equivalents	$ 177,677	$ 55,069
Short-term investments	77,495	93,901
Accounts receivable, net of allowance for doubtful accounts of $839 and $413	66,485	68,782
Deferred costs	14,252	11,898
Prepaid expenses and other current assets	5,078	5,079
Total current assets	340,987	234,729
Long-term assets
Property and equipment, net of accumulated depreciation and amortization of $25,394 and $21,924	10,592	10,437
Long-term investments	2,837
Deferred costs, net of current portion	18,779	17,182
Acquisition-related intangible assets, net	18,112
Goodwill	31,004
Other long-term assets	951	983
Total assets	423,262	263,331
Current liabilities
Accounts payable	8,492	5,598
Accrued payroll and other expenses	19,816	16,481
Deferred revenue	118,242	116,831
Deferred rent	1,000	892
Capital leases	25	21
Total current liabilities	147,575	139,823
Long-term liabilities
Convertible senior notes, net	109,772
Deferred revenue, net of current portion	5,919	2,470
Deferred rent, net of current portion	2,996	3,483
Capital leases, net of current portion	103	26
Asset retirement obligation	222	199
Total liabilities	266,587	146,001
Commitments and contingencies (Note 14)
Stockholders’ equity
Class A and Class B Common stock	5	4
Additional paid-in capital	371,491	314,301
Accumulated other comprehensive income (loss)	10	(110)
Accumulated deficit	(214,831)	(196,865)
Total stockholders’ equity	156,675	117,330
Total liabilities and stockholders' equity	$ 423,262	$ 263,331