Income Taxes Schedule of reconciliation of income taxes computed using the U.S. federal statutory rate to that reflected in operations (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Income tax benefit using U.S. federal statutory rate	$ (86,426,000)	$ (62,141,000)	$ (34,391,000)
State income taxes, net of federal benefit	(22,148,000)	(5,236,000)	(4,434,000)
Stock-based compensation	(5,909,000)	1,585,000	752,000
Research and development tax credits	(2,468,000)	(2,794,000)	(1,469,000)
Effect of federal tax law change	82,767,000	0	0
Other adjustments - ASU 2016-09 adoption	6,135,000	0	0
Change in the valuation allowance	(19,198,000)	48,096,000	39,291,000
Convertible note	47,016,000	0	0
Permanent items	543,000	53,000	26,000
Other	(312,000)	1,371,000	225,000
Expiring NOLs and credits - 382 Limitation	0	19,066,000	0
Income tax expense	$ 0	$ 0	$ 0