Equity Incentive Plans (Stock Option Activity) (Details) - USD ($)	6 Months Ended
	Jun. 30, 2020
Shares Underlying Stock Options
Outstanding beginning balance, Shares underlying stock options and restricted stock awards (in shares)	5,616,840
Granted, Shares underlying stock options and restricted stock awards (in shares)	806,923
Exercised, Shares underlying stock options and restricted stock awards (in shares)	94,219
Forfeited, Shares underlying stock options and restricted stock awards (in shares)	(2,883,533)
Outstanding ending balance, Shares underlying stock options and restricted stock awards (in shares)	3,446,011
Weighted- Average Exercise Price per Share
Outstanding beginning balance, Weighted - average exercise price (usd per share)	$ 19.50
Granted, Weighted - average exercise price (usd per share)	5.27
Exercised, Weighted - average exercise price (usd per share)	6.42
Forfeited, Weighted - average exercise price (usd per share)	19.43
Outstanding ending balance, Weighted - average exercise price (usd per share)	$ 16.59
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term	5 years 10 months 13 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value	$ 35,037
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Shares	2,144,609
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price	$ 20.84
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term	4 years 3 months 7 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value	$ 0