Unaudited Condensed Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Cash flows from operating activities:
Net loss	$ (7,184)	$ (6,384)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	3	323
Stock-based compensation expense	274	296
Write off of deferred offering costs	111	0
Changes in deferred rent	0	(57)
Changes in operating assets and liabilities:
Accounts receivable and unbilled services	0	448
Prepaid expenses, other assets, and deferred costs	(477)	(160)
Accounts payable and accrued expenses	186	1,052
Accrued severance and retention cost obligations	(1,809)	0
Deferred revenue	(64)	(65)
Net cash used in operating activities	(8,960)	(4,547)
Cash flows from investing activities:
Purchases of property and equipment	(14)	(171)
Net cash used in investing activities	(14)	(171)
Cash flows from financing activities:
Proceeds from employee stock purchase plan issuance	5	95
Net cash provided by financing activities	5	95
Net decrease in cash and cash equivalents	(8,969)	(4,623)
Cash and cash equivalents, beginning of period	46,985	32,243
Cash and cash equivalents, end of period	38,016	27,620
Supplemental cash flow information:
Cash received for interest	28	0
Noncash financing and investing activities:
Deferred offering costs included in accounts payable and accrued expenses	25	257
Equipment purchases in accounts payable and accrued expenses	$ 0	$ 25