Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 74,195	$ 31,014
Short-term investments, available-for-sale	304,996	162,795
Other current assets	4,883	4,394
Total current assets	384,074	198,203
Property and equipment, net	3,432	2,507
Long-term investments, available-for-sale	82,488	37,492
Restricted cash	4,791	4,831
Total assets	474,785	243,033
Current liabilities:
Accounts payable	2,561	246
Accrued liabilities	19,034	11,508
Current portion of deferred rent	269	119
Current portion of cease-use liability	428	467
Current portion of deferred gain on sale of real estate	3,423	3,324
Total current liabilities	25,715	15,664
Deferred gain on sale of real estate	10,898	14,322
Deferred revenue	10,231	0
Deferred rent	1,711	1,877
Cease-use liability	1,555	2,211
Other liabilities	221	260
Total liabilities	$ 50,331	$ 34,334
Commitments and contingencies
Stockholders' equity:
Preferred stock, $0.001 par value; 5,000,000 shares authorized; no shares issued and outstanding	$ 0	$ 0
Common stock, $0.001 par value; 110,000,000 shares authorized; issued and outstanding shares were 86,262,594 and 76,465,942 at December 31, 2015 and 2014, respectively	86	76
Additional paid-in capital	1,340,579	1,035,205
Accumulated other comprehensive loss	(977)	(277)
Accumulated deficit	(915,234)	(826,305)
Total stockholders' equity	424,454	208,699
Total liabilities and stockholders' equity	$ 474,785	$ 243,033