Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Cash flows from operating activities
Net loss	$ (18,829)	$ (66,319)
Adjustments to reconcile net loss to net cash used in operating activities
Depreciation and amortization	236	104
Stock-based compensation expense	4,976	7,522
Changes in assets and liabilities
Prepaid expenses and other assets	(124)	(7,124)
Accounts payable	(695)	1,194
Accrued and other liabilities	(860)	8,063
Income taxes payable		(247)
Net cash used in operating activities	(15,296)	(56,807)
Cash flows from investing activities
Purchase of property and equipment		(1,009)
Inducement on build-to-suit lease obligation	1,896
Net cash used in investing activities	1,896	(1,009)
Cash flows from financing activities
Proceeds from issuance of common stock in connection with employee benefit plans	35	2,399
Net cash provided by financing activities	35	2,399
Net increase (decrease) in cash, cash equivalents, and restricted cash	(13,365)	(55,417)
Cash, cash equivalents, and restricted cash at beginning of period	83,529	201,153
Cash, cash equivalents, and restricted cash at end of period	70,164	145,736
Supplemental disclosure
Income taxes paid		375
Supplemental disclosure of noncash items
Build-to-suit leasehold improvements	$ 5,428	1,219
Build-to-suit lease transaction		$ 8,174