Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 27,041	$ 17,425
Marketable securities	158,730	175,057
Accounts receivable, net	10,488	11,097
Deferred commissions	3,642	3,675
Prepaid expenses and other current assets	3,499	3,476
Total current assets	203,400	210,730
Property and equipment, net	3,497	3,630
Marketable securities, noncurrent	0	6,220
Deferred commissions, noncurrent	2,377	2,563
Other assets	78	131
Total assets	209,352	223,274
Current liabilities:
Accounts payable	4,169	3,217
Accrued expenses and other current liabilities	4,365	5,791
Accrued compensation	7,378	10,455
Deferred revenue	24,002	20,708
Total current liabilities	39,914	40,171
Deferred revenue, noncurrent	7,079	6,652
Other liabilities, noncurrent	226	261
Total liabilities	47,219	47,084
Commitments and contingencies
Stockholders’ equity (deficit):
Additional paid-in capital	398,941	393,397
Accumulated other comprehensive income	2	(40)
Accumulated deficit	(236,819)	(217,176)
Total stockholders’ equity (deficit)	162,133	176,190
Total liabilities, convertible preferred stock and stockholders’ equity (deficit)	209,352	223,274
Class A [Member]
Stockholders’ equity (deficit):
Common stock value issued	6	6
Class B [Member]
Stockholders’ equity (deficit):
Common stock value issued	$ 3	$ 3