Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Operating activities:
Net loss	$ (19,643)	$ (24,281)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	454	282
Stock-based compensation	3,869	2,553
Amortization of deferred commissions	857	1,376
Accretion and amortization of marketable securities	443	124
Expense related to warrant	0	2,429
Changes in operating assets and liabilities:
Accounts receivable	609	(1,250)
Deferred commissions	(638)	(282)
Prepaid expenses and other assets	30	(1,081)
Accounts payable	1,512	759
Accrued expenses and other liabilities	(4,403)	(3,376)
Deferred revenue	3,721	6,686
Net cash used in operating activities	(13,189)	(16,061)
Investing activities:
Purchase of property and equipment	(887)	(656)
Purchase of marketable securities	(13,034)	(35,733)
Sale of marketable securities	5,000	13,000
Maturities of marketable securities	30,180	5,000
Net cash provided by (used in) investing activities	21,259	(18,389)
Financing activities:
Proceeds from the exercise of stock options	1,640	1,522
Net proceeds from initial public offering	0	189,943
Payments of deferred offering costs	(94)	(2,102)
Net cash provided by financing activities	1,546	189,363
Net increase in cash and cash equivalents	9,616	154,913
Cash and cash equivalents at beginning of period	17,425	25,154
Cash and cash equivalents at end of period	$ 27,041	$ 180,067