Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 120,554	$ 159,678
Marketable securities	280,302	313,661
Prepaid expenses and other current assets	5,197	6,969
Total current assets	406,053	480,308
Property and equipment, net	2,945	1,897
Other assets	448	260
Total assets	409,446	482,465
Current liabilities:
Accounts payable	3,027	6,228
Accrued expenses and other current liabilities	16,545	14,952
Total current liabilities	19,572	21,180
Total liabilities	19,572	21,180
Commitments and contingencies
Stockholders’ equity:
Common stock, $.0001 par value; 200,000,000 shares authorized, 43,060,593 shares and 42,984,243 shares issued and outstanding at June 30, 2016 and December 31, 2015, respectively	4	4
Additional paid-in-capital	919,343	907,040
Accumulated other comprehensive income	188	5
Accumulated deficit	(529,661)	(445,764)
Total stockholders’ equity	389,874	461,285
Total liabilities and stockholders’ equity	$ 409,446	$ 482,465

Carrying value as of the balance sheet date of liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received that are used in an entity's business. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Carrying value as of the balance sheet date of obligations incurred and payable, pertaining to costs that are statutory in nature, are incurred on contractual obligations, or accumulate over time and for which invoices have not yet been received or will not be rendered. Examples include taxes, interest, rent and utilities. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).