Consolidated Balance Sheets - USD ($)	Dec. 31, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 48,642,225	$ 47,159,303
Investment securities, available-for-sale	335,458,459	428,041,021
Accounts receivable	94,339	30,660
Prepaid expenses and other current assets	4,005,093	8,025,147
Total current assets	388,200,116	483,256,131
Property and equipment, net	627,614	775,522
Other assets	75,765	71,875
Total assets	388,903,495	484,103,528
Current liabilities:
Accounts payable	3,754,647	1,632,905
Accrued and other current liabilities	5,329,293	3,423,464
Accrued employee benefits	1,448,394	1,207,143
Total current liabilities	10,532,334	6,263,512
Long-term deferred rent	2,868,622	1,597,105
Total liabilities	13,400,956	7,860,617
Stockholders' equity:
Common stock, $.0001 par value: 100,000,000 shares authorized; 43,292,906 and 43,155,875 shares issued and outstanding at December 31, 2016 and 2015, respectively	4,329	4,316
Additional paid-in capital	685,290,815	669,878,103
Accumulated deficit	(309,475,366)	(193,049,098)
Accumulated comprehensive loss	(317,239)	(590,410)
Total stockholders' equity	375,502,539	476,242,911
Total liabilities and stockholders' equity	$ 388,903,495	$ 484,103,528

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).

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

- Definition

Amount due from customers or clients, within one year of the balance sheet date (or the normal operating cycle, whichever is longer), for goods or services (including trade receivables) that have been delivered or sold in the normal course of business, reduced to the estimated net realizable fair value by an allowance established by the entity of the amount it deems uncertain of collection.