CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Operating activities:
Net loss	$ (52,535)	$ (63,396)
Non-cash adjustments reconciling net loss to operating cash flows:
Depreciation	138	139
Amortization of premium on investments	(232)	6
Share-based compensation expense	5,468	8,086
Changes in operating assets and liabilities:
Other current assets	(2,052)	571
Other long-term assets	(1,605)	1,134
Accounts payable, accrued liabilities and other long-term liabilities	(3,332)	3,834
Cash flows used in operating activities	(50,940)	(51,894)
Investing activities:
Purchases of short-term investments	(95,103)	(67,261)
Disposal and maturities of short-term investments	75,488	86,935
Purchases of property and equipment	(80)	(63)
Cash flows (used in) provided by investing activities	(19,695)	19,611
Financing activities:
Proceeds from sale of common stock, net	66,816	0
Proceeds from exercise of common stock options and warrants	2,149	2,355
Proceeds from stock issuances under employee stock purchase plan	71	237
Cash flows provided by financing activities	69,036	2,592
Decrease in cash and cash equivalents	(1,599)	(29,691)
Cash and cash equivalents, beginning of period	22,383	49,493
Cash and cash equivalents, end of period	$ 20,784	$ 19,802