Employee Stock and Benefit Plans (Stock Option Activity) (Details) - Stock Options - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Options Outstanding, Number of Shares [Roll Forward]
Number of shares, beginning balance	7,328	6,076
Number of shares, Options granted at common stock price	988	2,339
Number of shares, Options exercised	0	0
Number of shares, Options cancelled	(845)	(1,087)
Number of shares, ending balance	7,471	7,328
Number of shares, Exercisable	4,667
Number of shares, Vested and expected to vest	6,335
Options Outstanding, Weighted Average Exercise Price [Roll Forward]
Weighted average exercise price, beginning balance (in dollars per share)	$ 4.56	$ 5.47
Weighted average exercise price, Options granted at common stock price (in dollars per share)	2.33	3.17
Weighted average exercise price, Options exercised (in dollars per share)	0	0
Weighted average exercise price, Options canceled (in dollars per share)	4.67	6.68
Weighted average exercise price, ending balance (in dollars per share)	4.25	4.56
Weighted average exercise price, exercisable (in dollars per share)	4.92
Weighted average exercise price, vested and expected to vest (in dollars per share)	4.44
Weighted Average Fair Value Grant
Weighted average fair value grant, Options granted at common stock prrice (in dollars per share)	$ 0.81	$ 1.01
Options, Additional Information
Weighted average remaining contractual life, outstanding	4 years 4 months 24 days
Weighted average remaining contractual life, exercisable	3 years 8 months 12 days
Weighted average remaining contractual life, vested and expected to vest	4 years 2 months 12 days
Intrinsic value, options exercised	$ 0