Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Current assets
Cash and cash equivalents	$ 190,066	$ 55,069
Short-term investments	55,394	93,901
Accounts receivable, net of allowance for doubtful accounts of $317 and $413	56,022	68,782
Deferred costs	14,906	11,898
Prepaid expenses and other current assets	4,786	5,079
Total current assets	321,174	234,729
Long-term assets
Property and equipment, net of accumulated depreciation of $20,982 and $17,091	9,876	10,437
Long-term investments	7,979
Deferred costs, net of current portion	15,792	17,182
Acquisition-related intangible assets, net	19,517
Goodwill	30,572
Other long-term assets	1,036	983
Total assets	405,946	263,331
Current liabilities
Accounts payable	8,100	5,598
Accrued payroll and other expenses	21,450	16,481
Deferred revenue	116,610	116,831
Deferred rent	919	892
Capital leases	24	21
Total current liabilities	147,103	139,823
Long-term liabilities
Convertible senior notes, net	106,574
Deferred revenue, net of current portion	6,834	2,470
Deferred rent, net of current portion	3,237	3,483
Capital leases, net of current portion	117	26
Asset retirement obligation	205	199
Total liabilities	264,070	146,001
Commitments and contingencies (Note 14)
Stockholders’ equity
Class A and Class B Common stock	5	4
Additional paid-in capital	346,888	314,301
Accumulated other comprehensive loss	(53)	(110)
Accumulated deficit	(204,964)	(196,865)
Total stockholders’ equity	141,876	117,330
Total liabilities and stockholders' equity	$ 405,946	$ 263,331