Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
CASH FLOWS FROM OPERATING ACTIVITIES
Net loss	$ (44,490)	$ (32,207)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	699	1,075
Amortization of premium on investment	786	128
Amortization of discount on debt and capital leases	0	5
Amortization of debt issuance cost	0	39
Change in fair value of derivative liability associated with Medicis settlement	428	(47)
Stock-based compensation expense	6,229	4,724
Effective interest on financing obligations	217	100
Loss on disposal of fixed assets	0	29
Loss on impairment	1,949	0
Acquisition of in-process research and development	2,000	0
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(74)	(412)
Other non-current assets	0	(345)
Accounts payable	279	(938)
Accruals and other liabilities	(33)	2,337
Net cash used in operating activities	(32,010)	(25,512)
CASH FLOWS FROM INVESTING ACTIVITIES
Purchases of property and equipment	(994)	(2,292)
Proceeds from maturities of investments	46,050	0
Proceeds from sales of investments	1,000	0
Purchases of investments	(159,755)	(53,076)
Payment for acquisition of in-process research and development	(1,800)	0
Change in restricted cash	(145)	75
Net cash used in investing activities	(115,644)	(55,293)
CASH FLOWS FROM FINANCING ACTIVITIES
Principal payments made on capital leases and financing obligations	(1,725)	(956)
Net settlement of restricted stock awards to settle employee taxes	(341)	(620)
Principal payments made on notes payable	0	(2,652)
Proceeds from sale and leaseback financing	0	9,831
Proceeds from the exercise of stock options and employee stock purchase plan	938	587
Payment of registration statement costs	(182)	0
Net cash provided by financing activities	(1,310)	6,190
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	(148,964)	(74,615)
CASH AND CASH EQUIVALENTS — Beginning of period	201,615	171,032
CASH AND CASH EQUIVALENTS — End of period	52,651	96,417
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION:
Cash paid for interest	384	300
SUPPLEMENTAL DISCLOSURES OF NON-CASH INVESTING AND FINANCING INFORMATION:
Property and equipment purchases included in accounts payable and accruals and other current liabilities	90	20
Deferred offering costs	32	0
Holdback related to acquisition of in-process research and development	200	0
Write-off of fixed assets	$ 0	$ 28